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Патент USA US2374072

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April 17, 1945.
Filed Jan. 12’, '1943 >
6 Sheets-Shee't 1
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April 17,’ 1945.
Filed Jan. '12,‘ 1943
6 Sheets-Sheet 2 I
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April 17, 1945.
Filed Jan. 12, 1943
6 Sheets-Sheet 3
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Aprilvl'l, 1945.
Filed Jan. 12, 1943
6 Sheets~_-Sheet 4
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April 17, 1945.
Filed ~Jan. 12, 1943
6 Sheets-Sheet 5
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April 17, 1945.
Filed Jan. 12, 1945
6 Sheets-Sheet
//v l/EN TOR ‘
W. M. ‘BEA UM 0N T
Patented Apr. 17, 1945
' ium'reo ‘STATE
' .
., .7 1., ‘
Bell ' Telephone
M. Beaumont,
summimm J.,_assign'or
to: -,-' i I
New .York, N. Y., a corporation of New York
5 V;
, Application January12, 1943, serial 7N‘ 312,191" I)
20 Claims.
(01. 179-27!
' ‘
'cmiemmates the‘. more
sion efmeans'atthe secretary’s station for ‘pick
1 This invention relates to telephone systems and,
. particularly to central o?ice. and private branch
mg up'ahcla‘ll on‘ the key calling line extended
' thereto through the private ‘branch exchange and
‘exchange telephone systems of the type in/Which
an extension station of-the executivetype is pro;
vided' with facilities whereby connections to fre
which was, "‘held” by“ the’partyat' the key calling
quently called subordinate stations may VJbeQes-I '
tablished by-the party at the executive station .
,4 1;,
_ ; ‘Another feature .of the invention renders itpos;
siblej'forjthe ,secretary‘to'initiate outgoing ex
change calls overthelinevof'theykey calling sta
fore-in which subscribers having regular private .10 tion', When vthe party ‘at'the key calling station
wishesl't‘o extenda call through the private branch
branch exchange service are enabled to initiate
expeditiously and with a minimum of effort;
_ Telephone systems have been designed hereto
exchangetat?hichihis' line terminates, a partic
andcomplete calls-t0 other private branch exten
sion stations by the actuation of keys‘ individually
assigned to such extension stations; Such systems
have, been designed particularly for the purpose
mountingggil‘he actuation of; this key'vcauses a
of enabling an executive, or a high official to com
certain‘combinationfof positive and negativedi
ularkeyT assigned'for“. this ‘purpose ‘is actuated '
after the“ handset .has '. been removed from , its
municate with certain frequently called subordi~
rect current pulsesto be transmitted pvera conp- '
nates in such a manner ‘as to obviate the {necessity
trolicircuit?to. selectively ‘operate a corresponding
of the executive using the regular telephone dial,
combination .; of [register relays "which, vin turn,
functionitoe?echthe connection of the key .call
‘ing' ‘stationiline'to' thelline extending to. the private
branchzexchange. lhIn accordance with, the’ fea
or requiring the assistance of the-private branch I
exchange attendant \in completing connections
between his line and the linesof the frequently
turecf the inyentionunde'r instant discussion, the
connectiom'o?the ‘key, calling station line‘ with
called subordinates.‘ Systems of this type,» which
reduce to 'a minimum the requirements imposed
.on an executive subscriber in establishing connec
v.235 theLprivate branch _ exchangev line maybe effected
by the actuation of means. at the-secretary’s posi- '
tionswto the lines of a particular group of-subordi
nates; and which render such connections tofbe
completed in an expeditious manner; necessitate
vthe use of auxiliary equipment at the executive
‘station in the nature of a group of line selecting
tion,.which.means whenfut'ilized, simulates the op
erationiofitheparticular;key_vat the key calling
station and‘ causes the, operationof the same com~
bination; of gregjisteri'irelays and the consequent
connection of ,the'vprivate branch exchange line
I keys, and also of auxiliary switching apparatus
with the lineebnductors of the‘key calling sta
which responds selectively to the actuation ofthe
lineselecting keysto extend the executive's line to
‘the subordinate line correspondinglto the partic
ular line selecting ‘key actuated.
' -
*It‘is the object of this invention to'provide‘an \
improved telephone system of the key‘callingtype
brie?y’ defined. above and to further extend
tion.“ Thus the secretary has access to the pri
vatebranchpxchange lnot only, by ‘way ofjthe
secretary’s; own line butv also byway of the key
calling .stationiline, and may originatecalls ethere
overlwhen conditionswarrant it.
service. More particularly, the object of the in
iLAQfur-ther feature ofythe invention provides
means vwhereby the party at thekey calling station
may establish‘akey-initiated call to the line ex
tending}; to the secretary’sstationf Such‘acon
nection vis-_e_s,tablished_. in the samemannerias di
rect connections to'any other frequently called
vention is attained ‘by correlating the'equipment
privatelbranchextension;~ that is, by the actua
facilities afforded by‘ such a system.
' This object‘ is attained in accordancewith
feature of the invention by providing the-sub
scriber at a kev calling station with secretarial '
at a key- calling station with that ‘atasecreta'ry’s _>45
_ tion of, vatkey at the key calling station individ“
uallyia-assigned to the secretary’s line. " ‘
station "in such a manner that telephone‘ calls
originated at or incoming to‘ the‘ key calling- sta
a, A‘ still ifurther‘feature~ of the invention permits
calls aincomingover the secretary’s line to be
tion ‘may be handled by? a secretary when condi
“held?! byzthevsecretary and to be picked, up at
tions’ warrant such procedure. 'In'accordance
with this particular feature of the invention-a call 50 .the-key calling station.‘ ; _-In accordance with this
particular feature; when a call . on‘ the » secretary’s
on‘the-line' individual to the key‘calling station _
maybe picked up by'the secretary by the simple
act of operating a key at the secretary's station
which places the secretary’s ‘telephone inymultiple
with ' the ‘key: calling station line. . An ancillary 55
line is to'be transferred to; the key calling station
the secretary-places ya hold-condition on the line
and {disconnects her telephone therefrom. l v‘The
party at the key-calling station after removing the
telephone thereat from its mounting actuates a
key assigned especially for the purpose of picking
switches identi?ed and the ?fteen key-buttons
i up a ‘call which is “held” on the secretary’s line.
signed that whenever any one of the ?fteen key
buttons is actuated the switch SH is operated to
disassociate the telephone at station A. from the
line and the switch RA is operated to connect the
ground associated with contact I02 of the hook
constitute a key-set which is so mechanically de
The actuation of such key automatically places
the key calling line in multiple with the secre
tary’s line to thus e?ectively connect the key call
ing station to the line over which the call was ex
tended to'the secretary's line and‘maintains such
connection vin the cut through condition while
switch 100 ‘to the-contacts of the’ recti?er control
switches RI, R2, R4 and R8, it being understood
momentarily opening the connection towards the 10 that when the handset IBI is removed from its
secretary’s station to'automatically remove the
mounting the switch I00 is actuated to close its
1 hold condition placed on the connection by the
several contacts. The switches RI, R2, R4 and
secretary. Such a connection may be again ‘ R8 are disposed relative to the ?fteen key-buttons
= so as to be operated singly or in combinations
picked up by the secretary, in which case» the-con
nection of the secretary’s telephone ‘with her: line I 1-5 when the key-buttons are actuated. When the
switches RI, R2, R4 and R8 are actuated they
and the disconnection of the key calling station '
function to effectively connect the corresponding
result in the automatic release of the equipment
dry recti?ers I I, 22, 44 and 88 to the line con
utilized in extending the key calling line to the
secretary’s line.
ductors of the line KC. Switch RI serves to com- _
In accordance with another feature or the in
vention the apparatus. and circuits areso' ar
ranged that calls may be extended to the key
calling station when originated at other key call
plete the ground’ circuit to the tip conductor, T
of line KC through recti?er II ; switch R2 serves
the same purpose with respect to rectifier‘22';
switch R4 serves to complete the ground circuit
to the ring conductor R of line _KC through rectie
ing stations. Such calls are extended to the key
calling station by way oithe private branch ex
?er 44; vand switch R8 serves 'the'same purpose
relative to recti?er 88. At‘ P in Fig. 3 therev is
change line over which all calls directed to the
shown a source of alternating current which, as
key calling station arrive. When such'a'call is
will appear more fully in a later description, rm;
extended to. the key calling ‘station ‘the tip and
nishes current to the recti?ers II, 22, 44 and 88.
ring conductors of the said'line are physically
separated from their normal terminations ati'the 30 The table illustrated in Fig. 7 indicates the man;
her‘ in which the recti?er control switches are
exchange thereby isolatingithe ‘line, from the ex
operated in response to the actuation of each of
change. This feature provides secrecy on ‘con
the ?fteen key buttons.
nections involving two key calling stations and
'A separate manually operable key HA is mount
precludes the possibility of 'an attendantfat the .
exchange effectively associating her telephone set
35 ed on the telephone set atstation- A'a'nd acts as
with the connection for the purpose of eaves
a hold- key.‘ When actuated, it connects ground
dropping, Or for any other purpose." , ,1 , __ '_
‘to ‘the point‘ III] ‘or induction coil'ID to cause ‘dif
ferenti'al relay DF, Fig. 2, to, operate for a ‘pur
A ‘further feature of the‘ invention';contem—
plates the assignment of ‘a key ‘at the key calling
pose to be described in detail hereinafter. '
station to each of a one-way‘ line'circuitlto ‘the 40 ' The lower portion of Fig. 1 represents a secre
tary's station _S which is equipped with ‘a, tele
local exchange and a line circuit extcnding’to a
distant, exchange. Thus thejkey calling sub
scriber has access‘to the local exchange over a
plurality of lines andmay alsocomplete calls to
extension lines which terminate at an exchange
‘phone’ set comprising the handset I20, dial I2I',
ringer I24 ‘and induction coil I22. 'This tele
phone'set ‘is also equipped with a, series of keys
“mounted ‘on the base thereof such as keys KI, K2,
K3 "and I-IK;v the'last constituting" a hold key
which functions, when actuated, to place a hold
These and other features of the invention will
condition‘on the secretary’s private'branc'h ex
be readily’ understood from, the following de
scription made with reference tofthe accompany? .-¢; change line SL. The key KI serves to connect
the secretary’s telephone set with the line ~SL‘;
ing drawings, which when assembled in the mane
the key‘KZ' serves to connect the secretary’s tele
~ ner indicated in Fig. 8 constitute a circuit dia
phone set in multiple with the- line conductors‘ of
gram of a telephone system embodying the pres,
the key‘. calling station line KC; and the'key K3
ent invention.
serves to associate the secretary’s telephone with
Before 'entering'into a detailed'des'cription of
the line SLI to which the secretary may have ac
the method‘of operation of the system disclosed
cess. An auxiliary key CK, known as' a. i‘call”
in the drawings, a brief reference ‘to the equip—
key, 'is located at the secretary’s station S‘ and
ment furnished the'executive'station hand the
functions,‘ when operated, to extend the key'call
secretary's station S, and also‘ to the apparatus
controlled thereby‘ will beniacie. 'I'heupper por- , _ ing station Line'KC to the twoéway private branch
exchange line ZLX (Fig. 4). 'Thisvkey serves; the
tion of ‘Fig. 1 illustrates schematically the ap
same-general purpose with respect to‘ the score
paratus located at" the,key‘callingfstationn ‘asso
‘tary’s station S as does the No. 15- keyebutton at
ciated with‘ the line KC. ' This apparatus consists
station'A which serves to extend the‘ key calling
of a telephone set comprising the handset I‘Ill,
other than the local exchange.
, ,_
station line KC to the exchange PBX.
dial I09, ringer III, iriduction'coil ID and ~the
telephone hook‘ switch I00. Thesefeléments per- '65 ' Fig. 2, and the relays ST, LO, B, RLI and RL
of Fig. -3 constitute a supervisory circuit which
,form well-known functions‘. v In vpractice‘the tele
‘phone set may assume'tl'ie general appearance of
a standard "setand differs therefronlin thatlit
functions to provide all the supervisory, Signaling
and other features embodied in the key-calling
systemdisclosed, The lower portion-of Fig.1;
tons and a designation strip ‘which ‘bearsfadesig 70 ‘includes relays I,‘ 2, 4 and 8 which, constitutea
nation for 'each'key corresponding to the line-'to register circuit, ‘the said relays operating singly
which it is individually assigned. These key-but
or in combinations under the ‘control of the recti
‘tons are manually operable and‘contrbi'tnegop
?ér control ‘switches RI, R2, R4‘ and ‘R8 a's'indi
'cated 'by the table shown ‘in'Fig. 7. ‘ Theseiegis
'eration‘of four recti?er control swianes RI , ‘R2,
R4 and R8 and‘als'o’switches SHYind RA. The .75 . ’te'r relays‘ function to’ selectively controlthé op
has mounted on the base'there'of ?fteen keygbut4 , .
> 2,374,072
'eration‘of the connector relays ‘GT2,v GT4, GT5,
of l the ‘line jKG, and at H contact I I 02, it "connects
1 ground potential to the switch RA‘ 'which- switch,
GTSQGT'I, GT8, GT9v and GTHI, shown at‘the
left of Figs. 4, 5 and 6.. Each connector relay,
with the exception of relay CTIO, is equipped with
upper‘ and lower'sets of armatures, only one of'
which sets is effective at a time. Which set is
effective is determined by whether or not the
‘switching relay SW shown at the upper right
of Fig. 2 is operated. Each armature set of the
connector relays serves a particular line so that
each'connector relay other than relay GTI 0 serves
two lines.' The lines served by each connector
relay are indicated by the table shown in Fig, '7.
as hereinbefore mentioned, operates whenever
any- of the ?fteen keyebuttons of the telephone
set at the keyvcalling station is actuated for the
purpose of supplying ground to the rectifier key ,
pulsing equipment ‘indicated at KP; With the
telephone set bridged across the line ‘KG, relay L
(Fig. 2) of the supervisory ‘circuit operates in a
circuit extending from grounded battery, wind
' ingof relay L, back contact and third lower
armature of relay GO, back contact and second
lower armature of relay IG, back contact and
‘Connector relay GT2 serves the two-way private.
middle lower armature of relay TK, ring con
branch exchange line 2LX and the private branch :15 ductor R of the lineKG, through the closed sub~
scriber’s loop at station A, tip conductor Tlof
extension line XI with which the station IIX -
is associated; relay GT4 serves the one-way
private branch exchange line LX and the exten
sion line X2 with which the station 2X is‘ associ
ated; relay GT5 serves the extension line X3
with which the station 3X is associated, ‘and also
the multiple extension SX associated with the
secretary's line SL; relay GT6 serves the line
multiple SXI of the secretary’s line SL and the
extension line X4 with which is associated the
station 4X; relays GT1, GT8 and GT9 serve the
the line KG, outermost upper armature and back
contact of ‘relay TK, ?rst-lower armature and
' back conta'ct’of relay IGQto ground by way of
the second upper armature and‘back contact of
relay CO; Relay L locks under control of relays
TK and 10 in a circuit from grounded battery,
. winding and-?rst upper ‘armature and front con
tact of relay L, conductor 200, third lower arma
ture and back contact of relay TK, to ground by
way of ‘the’ back contact and second upper arma
extension lines X5, X6, X1, X8, X9 and ,Xl0 with
which the stations 5X, 6X, 1X, 8X, 9X and‘ IOX
ture of relay IG.
respectively,- are associated; and relay‘ CTN)
B (Fig. 3) and relay PB (Fig. 4) operate. Relay B
With relay L‘operated. relay C, (Fig, 2), relay‘
serves the line DPX which terminates at‘ a dis 30 operates in an obvious circuit which includes the
tant private branch exchange.‘ The various vpri- 4
third outer armature andfront contact of relay
vate branch exchange lines and extension sta
tions are illustrated terminating in jacks at. the
L. Relay G operates in an obvious circuit which
exchange terminations being‘ shown forthe sake
tact of relay H2, conductor 400,'back contact and
?rst lower armature of relay GT2, conductors
includes the middle upper armature and front
local manual exchange PBX. It is to be under
contact of relay L. Relay PB operates in a cir
stood that such lines may well terminate in 35 cuit extending from grounded battery, winding
switch terminals ‘at a dial‘ exchange, the manual
ofrelay PB, ?rst lower armature and back con
of simplicity of disclosure only.
; '
At the upper right corner or Fig. 4‘ there is
‘500 and 2M, front contact and second lower
diagrammatically indicated the equipment of an ~40 armature of relay L to ground. ‘This circuit also
other key calling station. This showing contains
now ?nds ground-at the ?rst upper armature
a- single connector relay GT which,‘ in practice,
would correspond to one of‘the connector relays
and front contact of relayB.
At its second upper and lower armatures relay
of the key calling equipment associated “with sta
G, operated, opens the tip and ring conductors
way‘ of the two-way private branch exchange
line 2LX.
armature and front contact, relay Goonnects
tion A. This relay functions to extend a call 45 to the tripping circuit which includes the lower
from ‘another key calling station to station A by ' winding of tripping relay TR. At its ?rst lower
ground to conductor 204 which, serves as a hold
ing ground for the register relays I, 2. 4 and 8,
wits and apparatus ‘illustrated, the method of 50 and at its ?rst upper armature and‘ front con
‘II-laying described, in a general way, the cir- ‘
operation of the disclosed system‘ will now’be
described in detail.
Call to private branch. exchange line '
tact it completes an obvious’ operating circuit v
“for relay GO.
Relay PB (Fig. 4) operated, connects battery
to the sleeve contact of jack JA which termi
In making a call to a station to which the
party at the key calling station A does not ‘have
nates the two-way line-circuit 2LX at the pri
vate branch exchangePBX thereby rendering
the line busy to the private branch exchange
equipment. This battery connection is made by
direct‘ access. that is, to a station which is not
represented by any of the key-buttons of the
way of the upper armatureand front contact
telephone ‘set at the key calling station, it is nec ~60 of relay PB and resistance 05L It is to be un
essary that such a call be extended automati
derstood that the jack terminations of the vari
cally by way of the regular automatic switches
ous lines at the exchange, have been illustrated
at‘v the-private branch exchange, or through the
for reasons of simplicity only, and that should »
medium. of the operator at the exchange in the
such lines terminate in a dial exchange the busy _
case of a manual exchange. To initiate such'a
call, the party at the executive or key calling sta
tion removes the telephone handset at station A
from its mounting and actuates key-button No.
15 which in the drawings is assigned to the pri
vate branch exchange line 2LX.
condition produced by relay PB would be 're- .
?ected in the‘ automatic switch thereatto render
the key calling, or executive’s line busy to this
equipment. At its lower armature and front COD",
tact relay PB places a similar busy condition on
I When’ the handset I0! 5is removed from its
mounting at station A, the switch I00 is actu-.
the, lead 43| which extends to the equipment atv
ated. This switch e?ectively connects the'tele
phone transmitter and receiver of the‘ handset’
Relay CO, the register connector relay, op
erated, extends the-tip and ring leads. T and R
‘l0! acrossthe tip and ring conductors'T-andR
of the station Ato the conductors 3'01 and 300',
another key calling station.
respectively, which connect _- with the register
which,‘ with-relay GT2 operated, is-extendedgto
circuit comprising relays I, 2, 4 and 8. The ring
the. middle lower armature and back contact
the exchange line circuit 2LX. Relay _TK, op
erated, also opens the locking circuit for relay
L which relay restores its-armatures. Relay B,
of relay TK; the second lower armature and back
contact of relay IG, and the third lower arma .5 however, does not release since it isnow held
ture and front contact of relay CO, whereas the
operated under control of relay L2 in the ex
lead R is connected to the lead 380 by way of
change line circuit 2LX as will now'be described.
tip lead T is connected to the lead 3M by way
-When the relay GT2 operated to extend the
of the third upper armature and back contact
link KL to the line circuit ZLX, relay L2 operated
of relay TK, the ?rst lower armature and back
in a circuit which may be traced from grounded
contact of relay IC, and the. second upper arma- ‘
ture and front contact of relay GO.
Thus the
register circuit is effectively connected to the
battery, winding of relay L2, back contact and.
second lower armature of relay SL', winding of
relay Ll, front contact and third upper armature
of relay GT2, conductor 405, back contact and
calling line when the handset at station A is
removed from its mounting.
15 ?rst lower armature of relay SW, conductor 2I4
At its ?fthupper armature and front contact - of link KL, front contact and second upper arma
relay GO connects ground to lead 206 and thence
ture of relay HR, upper winding of relay DF,
by way of conductor 201, normal contacts 208
?rst upper armature and front contact of relay
, of tripping relay TR to the motor startlead 205
TK, front contact‘and second lower armature of
which results in the operation of the ringing
relay TK, ring conductor R of line KC,~ closed
machine included in the equipment shown
subscriber’s loop at station A, tip conductor '1‘
schematically at PS in Fig. 2. At its middle up
of line KC, third upper armature and front con
per armature, relay CO completes an obvious
tact ofrelay TK, front contact and ?rst lower
operating circuit for relay PR. At its fourth
armature of relay TK, lower winding of relay
upper armature and front contact and its fourth 25 DF, ?rst upper armatureand back contact of re
lower armature and front contact, relay GO com
lay HR, conductor 246 of link KL, second upper
pletes a circuit from the alternating current
armature and back contact of relay SW, con
source P (Fig. 3), by way of conductors 302 and
ductor 406, fourth upper armature and front
394’ and full-wave recti?er 353 to the point 305
contact of relay GT2, conductor 484, ?rst upper
of the register circuit.- This power source P 30 armature and back contact of relay SL' to
furnishes-current to the register relays l, 2, 4,
ground. Relay B is held operated in a circuit
and 8, which operate selectively under the con
extending from grounded battery, winding of re
trol'of the key-buttons at the calling station A.
lay B, conductor M2, second lower armature
At. its second lower armature and front con
and front contact of relay GT2, conductor‘ 4-! I’,
tact relay GO prepares an operating circuit for 35 back contact and second lower armature of ‘relay
relay LO by connecting one terminal of the relay
H2, front contact and second lower armature
winding‘ to the lead 306 which terminates inone
of relay L2 to ground. Thus relay B is held
of the front contacts of power failure relay PF2.
operated and maintains the circuitsin the out
It will be observed that the power source P nor
through condition. Relay Ll operates in- the
mally furnishes operating current to the wind 40 circuit traced for relay L2 and maintains the
ing of relay PF! by way of the full-wave recti
relay HI short-circuited.
- ?er 301 so that this relay PFI is held operated
Relay L2 at its ?rst lower armature and front
so long as there is no power failure. This relay
contact connects ground to the ring conductor
controls the operating circuits to relays PF2
439, extending to the exchange, by way of resist
and AC so that as long as relay PFI is operated 45 ance 409, and the second lower armature and
the relays PFZ and A0 are deenergized. In the
back contact of relay COL. This ground, as will
event of a power failure, relay. PF! releases its
appear from a later description, brings in a lamp
armatures thereby causing relays PF2 and AC
signal at the exchange PBX, or in the case‘ of a
to operate, the latter functioning as a buzzer
dial exchange causes the line switch to start op
signal to audibly indicate the power failure.
erating in a well-known manner. Thus, in the
Relay PF'2 in operating, connects ground poten
event of a failure of the power source P, a call
tial to a plurality of leads, such as 386, each of’
which is initiated at station A is automatically
which extends to a different relay LO associated
extended to the exchange over the two-way line
with the supervisory equipment serving different
circuit ZLX.
key calling stations. Thus should there be a 55
Time out
power failure at the time a key calling station
initiates a call, the relay LOv corresponding to
the calling station would operate over the lead
At its ?rst upper armature and front contact
relay CO completes an operating circuit for re
lay S'I‘ which relay in operating performs no use
306 and the corresponding contacts of the re
lay CO.
60 ful function at the present time unless the calling
party fails to actuate a line selecting key-button
Relay LO under the condition of power fail
within a predetermined period of time following
ure functions to automatically extend the calling
the removal of the handset “H from its mount
line KC to the exchange ‘PBX by way of the
ing. The description is continued under the as
two-way private branch exchange line circuit
2LX. More particularly, with relay LO operated 65
due to the power failure, relay GT2 (Fig. 4) 0p
sumed condition of no power failure.
Should the calling party at station A fail to
operate one of the key-buttons within-a given in
I crates in a circuit extending from grounded
terval after starting a call by removing the hand
battery, winding and normal make-before-break
set at the calling station from its mounting, the
contacts of relay GT2, conductor 40L conductor
335, front contact and upper armature of relay 70 circuit functions to release the register circuit
from the calling line. More particularly, when
LO, front contact and ?rst lower armature of
relay L to ground. At its ?fth upper armature
relay CO operated as described above, an operat
relay GT2 causes relay TK to operate which
ing circuit for relay RL (Fig. 3) is completed
disconnects the register circuit from the calling
which includes grounded battery 308, resistance
line KC and extends the latter to the link KL 76 3l3, winding of relay RL, thermistor 310,,normal
make-before-break contacts of relay RLl,.-,con¢
before-break . contacts ‘of relay RLI .' conductors
ductors3~l land 3|2, front contact and ?rst ,up
perarmature of relay CO and associated ground.
When this circuit is closed, the resistance of the
thermistor 310- is high and relay RL does notre
ceive sufficient current to operate. After a,time
3H,, and 3l2,¢front contact and first upper arma
ture ofyrelayqco. toground. Thus, relay LO will
not eperate ‘and the call will progress in a normal
interval, the resistance of thermistor 3l0 becomes
. low enough to permit relay RL to operate which,
in?turn, operates relay RLI in an,_obvious¢_cir_,
,; When ‘lieyrbutton No. 15 is actuated, the 'varis'e
tor'or recti?er ‘controlling contacts RI, R2, R4
andlRtd’ are, , closed‘, V as" indicated by‘ the table
shown 'in'TFig. 7,’ to e?ectively connect the recti
cuit. ' Relay RLI operated connects thewinding
ofrelay ST in series ‘with the thermistor >3l0 in
v10 ?ers'll, .22, 44 and‘88'to the conductors of line
at potentiometer circuit. The potentiometer-elm
andv switch. SYH is opened whenever ‘any one of
.cuitrincludes battery 3|5, resistance, 314. to the
point 316 where it divides, one branch extending
to ground by wayof resistance 399, upper arma
KC. 'It' ‘is understood that switch'RA is. closed
the key-buttonsis actuated. In accordance with
the tablefsh'own in Fig‘. 7,.reg'ister relays l', 2, 4
and" ‘Bf'oPe'rateWhen the‘i‘ectl?elf controlling con
tactsj'Rl, R2,"R4'ah‘d'/R8 are closed in response
ture and front contact of relay RL and. conducs
to'th'efactuation Of key-button No. 15.' tor 3,12, another branch including the winding of
_, "Due" ‘to the Tclosure'of'rec'ti?er controlling'con
relay ST, thermistor 310, upper armature and
tact "Rl‘,,_register "relay '1 , operates in 'a' circuit
, front contact of relay-RL-l, conductorstll and
312, front ‘contact and ?rst upper armature of 20 which , may be? traced ‘ from ground, jswitchhook
contact"! 02 ‘at station‘ A‘; switch‘RA, recti?er con
relay CO, ‘to ground. Thus the current in ther
trolling switch‘ Rl‘jpositive' poled recti?er ‘l'l,
mistor 3l0 is reduced and the thermistor will
vcool- off, increasing its resistance. . When this
switchho'ok‘ contacts vI05, conductor I06, tip‘con
‘d’uct’jo "jTofline KC,'third upper armature and
lease causing relay L0 to operate in a circuit _ back‘ contact‘o’f relay TK, ?rst lower armature
current reaches a certain value relay ST will re
extending from grounded battery, winding ofre
lay LO, back contact and armature of relay ST,
‘front contact and lower armature of relay RLI,
“conductor 204,‘- iirst lower armature and front
an‘ back’ 'e‘ontactoffrelay 10, second upper ar- '
,r'nature and irontcontact of relay C0, conduc
tor 30l' lower winding‘ of register, relay I, positive
poled recti?ers3l8 and 319, conductor 320', rec
contact‘ of relay C to ground.‘ With relay ,LO 30 ti?eri32l"ofyfullfwaverectifier‘ 303, winding of'
relay FEW; recti?er ‘322, conductor 304, front con
operated, relay CT2 (Fig. 5) operates in a circuit
extending from grounded battery, winding of re
tact and fourth lower armature of relay CO, front
jcontactand fourth} upper armature of relay CO,
lay, CTZ, normal make-before-break contactsof
cond,"p_ytorgv302,jalternating current source P to
relay CT2, ‘conductors 40! and 335, front contact
and upper armature of relay LO, tovigroundv by A, ground Relay’ I" operates in this circuit on the
way of the front contact and ?rst lower arma
positive‘pulses transmitted over the tip conduc
ture. of relay L. At its second lower; armature
and front contact relay LO locksv to ground at
' ' 15 Register - relay
2 operates in‘ a circuit extend
.the front contact and lower armatureof relay B.
' Relay GT2, operated, causes relay TK (Fig.7 2_)
to operate in a circuit which is traced from
metrical-ground; switchhook contact 102, switch
(RA); re'cti?ercontrolling switch R2, negative poled
‘grounded battery, winding of relay TK,,co'nduc
403, tip conductor T of line KC, third upper 'ar- .
tor 2| I, back contact and third upperarmature
‘of relay SW, conductor 2l2, ?fthIupper-arma
armature ‘and'back‘contactof relay 10, second
recti?er 22,- ‘switchh'ook' contacts ‘ I05, conductor
mature vand~back contact of relay ,TK, ?rst'lower
'/'ture and front contact of relay CTLto ground. .1; *upperarmature ‘and front contactv of relay ' CO;
RelaylTK, operated, disassociates the tip and ring
conductors T and R of the line KC from the
conductors 300 and 3M which extend to the reg
istercircuit thereby disconnecting ‘the. register
ductor 30!‘; negative poled recti?ers 323 and
lower ‘winding-10f relay 2 ‘to the point 305,‘
lc'onductori 3320, and‘ thence to ground‘ through the
source?‘ by "way of‘ the circuit previously de
Fscribed-v inrconnection ‘with the" operation vof‘ rel'a'y
from the calling line. Relay TK also opens-the
locking circuit for relay L causing thisrelay to 6.0 vl",*-eirceptvthat the'recti?ers 344 andj345 of'full
restoreiits armatures. Relay L releases relays B
'wa'vel' recti?er 303 are substituted, for recti?ers
‘32»l'¥a-'nd1'>322. Relay 2 operates in'this‘ circuit on
and C. Relay B releases relay L0 and causes. re,
the ‘negative impulses transmitted over the ‘tip
lay CT: to be deenergized. The ‘circuit'is'. thus
restored to normal.
It is assumed in the preced- ,
ing description that the party at the station A‘
‘conductor’? of line KC.
- The operating circuitfor register relay 4ex
replaces the'handset before actuating a key-but
ton, in which case the relay L2 would notop
erate to hold relay B operated. Otherwise ‘the
~~tendsi>froin ground, switchhook contact "I02,
line KC, is extended to the exchange in the man
nerdescr'ibedin connection with a power failure.
ductor Rof'the line KC, ‘n'iiddle lower armature
Ordinarily the party at the key calling- station
will operate one of the key-buttons to complete
afcall before the timing circuit releasesrelay‘ST.
[In the following description the calling'party; is
assumed to have operated the No. .15 key-button‘
immediately after removing the handset from
its mounting at station A.‘ ‘Obviously then, ‘when
relay CO operated, as, hereinbefore described, to
s'witchiRA,'-recti?er"controlling switch R4‘, nega
j-tive'poled rectifier ‘4-4, ‘conductor ‘I08, ring con
'andbackjcontact of relay TK, second lower arm'aé
"turei a‘n'd?-back- contact'of relay ‘IC, third‘lower
"armature and front contact'of relay CO, conduc
tor 300;-‘to'~the point 325, thence through negative
poled rectifiers326 and 321,:lower winding. of me
isterlrelay "4,>'to the point 305,‘ conductor 320'and
:then‘ceto the grounded source P by wayfof the
circuit previously described in ‘connection .with
.the operation‘ of register relay‘ l. ' Relay 4 there
‘ complete an operating circuit for. relay HST,‘ the 70 fore operates on the negativeimpulse transmitted
timing circuit including thermistor‘ 310 will not
have su?icient time to cause the release of. relay
ST’so that this relay’remains operated in; a cir
(extending from grounded battery-r315, re
sistance 3 I74. Winding. of relay -S.T.,n0rma1 make
over the ring conductor R of the line KC. .
' ' '
. vlinegister relay _8 operates 'inva’circuitextending
from-ground, switchhook contact I02, switchRA,
: recti?er controlling switch 1R8, positive‘ poled rec‘
~tifier~_,p8,_8,v conductor 1 08,: ringcondu'ctor R > or‘ the
line KC, middle lower armature ‘and back contact
front contact of relay '1'K,front contact and sec;
ond lower armature of relay TK, ring conductor
R of line KC, through the closed subscriber loop
at‘ station A, tip conductor T of line KC,'third
upper armature and front contact of relay TK,
of'relay TK, second‘ lower armature and-back
contact of relay IC,,third ‘lower armature and
front contact of relay CO, conductor‘ 300; to the ~
point 325, thence through the lowerwindin'gof
"relay 8, positive poled‘ recti?ers- 329:_and 328 to
front contact and ?rst lower armature of relay
the point 305, conductori32llyand thence to the
grounded source'P by way of the circuit previously
TK, lower winding of differential relayDF, ?rst
upper armature and back contact of relay HR,
traced for relay 2. Relay 8 thus voperates on the
positive impulse transmitted over thering con
tip conductor 216 of link KL, second upper arma
ture and back contact of relay SW, conductor
406, fourth upper armature and front contact
of relay GT2, conductor 4B4, ?rst upper armature
ductor R of line KC.
‘ '
Register relays l, 2, 4 and 8 ‘in actuating their
respective upper armatures to close contacts 330,
and back contact of relay SL' to ground. Relays
L2 and LI operate in this circuit but relay DF,
33!, 332 and 333 lock to ground at the front'con
‘tact and ?rst lower armature of'relay‘C by way 15 being differential, does not operate at this time.
Relay Ll short-circuits the winding of relay HI‘.
of'common conductor 20,4. " It will be noted‘ that
- When relay L2 operates it completes an oper
during the period that key-button‘ No, 1515 actu
ating circuit for _’ line relay 40"! which extends
ated and the operating impulses traverse'the cir
‘from grounded battery, right winding of relay
cuits traced for relays l, 2,14 and f8; relay FW is
operated and holds its armature disengaged from
401,"?rst armature and back contact of sleeve
relay 40B, ring-conductor 439, second lower ar
its working contact. When‘ the key-button is‘ re
mature and back contact of relay COL, resist
leased and the impulses cease toi?ow, relay FW
restores its armature to extendfthe' ground at .
ance 489, ?rst lower armature and ‘front contact
of relay L2 to ground. Relay 40'! operates in
the front contact and ?rst lower ‘contact of re
lay L to the conductor 334,'this‘ ground constitut 25 this circuit and completes an obvious circuit for
line‘ lamp 410.
ing a functional ground which ‘serves to operate
It is to be understood that the ground applied
the connector relays, such as ‘GT2, as‘ presently
will be
to the ring conductor 439 would serve in a dial
exchange to start a line ?nder operating in the
With register relays l, 2, 4 and S'Aoperated and
locked, and with relay FW released. relayQCTZ '30 well-known manner to seize the calling line.
At its second lower armature and front ‘con
operates in a circuit extending from grounded
tact relay L2 extends ground over a circuit which
battery, winding and normal make-before-break
includes the second lower armature and back
‘contacts of relay CT2, conductor 40!, conductor
I 335, front contact and second lower armature of _ € contact-of relay H2, conductor 4H, front con
‘relay‘l, contact 336 of relay .2, contact 33'l'of’ relay '35 tact and second lower armature ‘of relay GT2,
conductor, M2 to battery andground through
[?rst lower armature and front contact ofrelay
the winding of slow-to-release relay B to main
8, conductor 23!, conductor 334, back contact and
armature of relay FW, back contact and upper
armature of relay LO, front ,contact' and first
tain relay B operated.
- '
ture,‘ relay GT2 opens theroperatingpircuit for
relay PB'in the privatev branch exchange line cir
manner. After the seizure of the calling line by
; Upon noting the lighted signal 410 the private
V40 branch exchange operator would insert plug PA
lower armature of relay L to ground.
into jack JA associated with the lamp signal 4H)
Relay GT2, operated, locks by way of its ?rst
to'handle the call in the usual manner.
' upper armature and front contact, conductors
When relay TK operated, it caused the release,
500 and 20] to ground ‘at‘the front contact and
directly or indirectly, of relays L, ST, RL, RLI,
‘?rst upper armature of relay B. At its fifth up
per armature andfront contaqt relay C,T2'_com_ 45 C, 'CO and the register relays i, 2, 4 and 8. Re
lay~B, however, as indicated above, is held oper
pletes an operating circuit forrelay 'I'KlFig. 2)
which extends from grounded battery, winding
--~It isl‘to be understood that should the calling
of relay TK, conductor 2| [,back contact v and
line terminate at a dial exchange, the party at
third upper armature of‘r'elayl‘SW, conductor__2|2
and the ?fth upper armature and frontcontact 50 station A would proceed to complete the initiated
c‘allby-operating the dial 189 in the well-known
voi‘ relay GT2 to ground. At ‘its first lower arma
cuit ZLX causing this relay tol restore ‘its, arma
tures. At its third and fourth upper varmatures
and front contacts relay CI’YI‘2 extends the link
KL (Fig. 2) of the supervisory circuit to ,thepri
vate branch exchange line circuit 2L_Xwhich, as
shown in Fig. 4, terminates at the exchange, PBX
the line-finderv in the exchange the operation of
the dial would set the automatic switches at the
55 exchange in the well-known manner to extend
the calling line to the line of a called subscriber
whose telephone designation is dialed by the
‘calling party‘ at station A.
However, when in response to the lighted
in the jack JA. This line. circuitmay well termi- ' 60 lamp signal 410 at the manual exchange illus
trated, the attendant thereat picks up the call in
nate in the terminals of a lineswitch at an auto
the manner indicated above, relay S operates
matic or dial exchange but as hereinbefore ex
from battery on the sleeve of the plug PA, over
plained, it is shown‘ terminated at a' manual office
the sleeve terminal of jack JA, upper armature
merely to simplify the disclosure.
and back contact of relay PB, ?rst upper arma
With relays TK_ (Fig. 2) and GT2‘ (Fig. 5)
ture and back contact of relay COL to ground
operated, a circuit may be traced from'grounded
‘through the winding of relay S. Relay S, oper
battery, winding of- relay L2, conductor 402, back
ated, ‘closes an obvious operating circuit for re
contact and second lower armature of_ relay SL’,
lay SL'. Relay SL' at its ?rst upper and sec
winding of relay Ll‘, front contact and third upper
70 ondlower armatures and front contacts closes
armature of relay GT2, talk, conductord?i, back
contact and ?rst lower armature of relay‘SW, talk
conductor 214 of link KL,,backcontact and sec
ond upper armature of relay HR, upper winding
of di?erential relay DF, ?rst upper armature and
vthe talking circuit from the exchange through
to ‘the calling station A and at its second upper
‘armature and front contact it connects ground
to the lead 41 I by Way of the second lower arma~
'ture and back contact of relay H2, which ground
serves to hold relay B (Fig. 3) - operated which,
‘HR in which r919‘? HR Operates. “Banana-at
in turn, holds the equipment in the cut-through
condition. Relay 7L2 releases when relay SL’
its second upper armature opens the5 ring con
ductor 2“ to the station Aland at its. front con
tact and same armature connects battery "2-18
thereto. At its ?rst upper armature-‘l and back
‘On a manual connection the calling subscriber
informs the exchange attendant of the tele
contact relay HR opens thetip lead 216 and at its I
phone number of the desiredcalled' party and
front contact and same armatureconnects ground
the attendant extends the connection in the
to the tip lead. to'thecalling station. . Thus, bat
usual manner.
tery and ground are.connected-throughthe. wind~
ings of the differential relay DE‘. to the ‘key calling
The insertion‘of plug PA into Jack JA of ‘the
calling line causes the lamp» signal 410 to be ex
‘tinguished in the well-known and obvious man-'
ner. Relay S operated, connects busy battery
to the‘ lead 4'3]v extending to the equipment at
another key calling-station.
station tomaintain a balanced line while the
hold key is operated and to prevent-the line of'the
key calling station being connecte'd'to‘the regis
> “
ter circuit until the hold‘ key is released; v
' Atlitsrcontacts 220Vrelay‘ H connects-‘the tip
lead 2|6 extending’ towards. the private branch
At the termination of the call between the
exchange 'to1 the hold- lead 222 to-effect the fol
key calling station A and the desired private
lowing bridge eircuit: from the tip terminal'of
branch exchange extension station the party at
jackv JA, back contact and ‘second upper arma
station Areplaces the handset ml on its mount
ing, the private branch exchange automatic 20 turerof relay COL,.front contact'iand ?rst-upper
armatureof relay SL3 conductor #04, irontcon
equipment or the attendant, depending on
tact and fourth upper armature "of »--»relay- GT2,
whether the exchange is of the‘ dial or manual
conductor 406,7 back Jcontactv and- second. upper
type, opens the sleeve circuit‘ causing» the re
armature of vrelay SW,- contacts-1200f relay kH,
lease of‘rel'ay S, which relay, in turn,‘ releases
- second lower-armature andback' contact of relay
relay SL'. Relay SL' releases relay’jB ‘which,
SW, conductor 222,.{second‘upper armature ‘and
at its ?rst upper armature and front contact
opens the locking‘circuit to relay CT2 which re
lay, in releasing, opens the operating circuit for '
front contact-of relay ‘GT2, conductor-4| 3, wind
ing of relay Hl,resistance 4“, third lower arma~ '
relay'TK thus restoring the apparatus to nor
The same release operations described above
in‘ connection with the manual exchange will
be performed in the event the establishd con
nection tothe called line is completed by way of
the automatic switches at a dial exchangeland
released when the calling‘ partly disconnects.
ture and front contact of'relay SL', ?rst lower
armature andback contact‘ of --relay.._COL, con
ductor 439 to .the ring terminal of jack JA.. vRelay
L1 ‘is, of course,“ deenergized at this time due to
the operationloffrelay HR." The bridge circuit
just- traced serves as 1a holding ‘bridge‘ito hold
the established‘ connection. ‘Relay HI‘ operatcsin
this circuit from battery atwthe ‘exchange-and. at
its ' second upper armature-and _ front-contact? es
_Holdingvby key calling subscriber
tablishes an obvious operating circuit iforrelay
H2. Relay HI‘ at-its ?rst vupper armature and
Should the party at the key calling station A,
for any reason, desire to hold the connection 40 front contact connects its own winding directly
acrossvtheexchange end of the establi'shedcon
the completion of which was-described above,
n'ection. Relay H2'at its second‘lower armature
the hold key HA at the key calling ‘station is
and 'back contact removes the ground atithe sec
actuated to its closed position. This key oper
ation connects ground 'by way-oi switchhook
ond upper armature and fronticontactof relay
contact I02 to the terminal H0 ofinduction coil " SL' from conductor 4H which,‘ by way ‘of-tthe
11) which point 'is common to. both the tip and
from, contact and ‘second lower-armature of-relav
ring conductors-T and R of the line KC so that
GT2 and conductor “2 was extended to .theiwind_ -
. ing of relay B. Thus relay B is deenergized-and
ground is now connected to both these conduc
releases its armatures. At its; ?rst .u'pper arma
tors at the calling station. It will be observed
that the differential relay DF has its two wind 50 ture and front contact relay B opens the locking
circuit for. relay CTZ whichi relay‘restores its .
ings included in series in the line conductors of
the talking connection and through current
traversesthe windings of the relay at this time
from the exchange battery the relaydoes not
.operate due to the differential action of the reg
lay coils. However, when ground is’ connected
armatures. Though relayrCTZ at-;its ?fth upper
armature. and front contact opens: the" original _
operating circuit for relay TK thisplatterirelay
55 is now held operated under control‘of relay HR.
Thus the connection is held dueto the operation I
to the tip and ring conductors of the line at the
of the hold key HA at station A.
, .
< .
When the hold key HA at station A is released
calling station due to the operation of hold key
relay 'DF releases due to the differential action
HA, the current ?ow in‘ the windings of the
differential relayDF is unbalanced'an'd the re-v 60 o'fits windings‘ and in restoring its armature it
lay operates. .The hold’ key HA _‘effectively. opens the operating circuit to relay H. Relay H
restores its armatures thus opening the operating
shunts one winding of the relay. Y‘ Transmission
circuit for relay HR which causes relay TKto re
lease and also opens the battery and ground con
relay DF. " Due to its being differentially con 65 nections to the windings of differential relay DF.
The release of relay TK-bringsin the start con
nected there is no transmissionloss. in the relay
‘battery is furnished the calling station from the '
vexchange through the windings of differential
except by the direct current resistance.
V .
dition causing the .key calling station to be re- ‘
Relay DF, operated, causes relay H to operate
connected to the register circuit so that anotherv
call may be made by the party at station A,’ if
in a circuit extending from grounded battery,
"winding of relay H, conductor 200, ‘front contact 70 desirable. When the party at the key calling
station wishes to release the hold condition and
"and armature of relay DF, conductor 2H, to
ground byway of the ?rst‘ lower ‘armature and Y
backv contact of relay L0.-v Relay H locks under
control of relay ‘B and, at'its uppen armature,
completes an obvious energizingl circuit for vrelay
again talk on the connection held, the call is
picked up in the regular manner. More par
ticularly, the No. 15 key is again actuatedto cause
the selection of. the private branch eXQhange line
2L)! in the manner previously described. When
such ‘a call is to be reestablished and the No. :15
key-button is actuated the connection progresses
in vthe manner previously described and when the
CT2 and TK relays operate to connect the calling
station through to the exchange, relay Ll (Fig. 4)
operates over theclosed subscriber’s loop and, in
operating, relay Ll short-circuits relay HI which
relay releases and, in turn, releases relay H2 thus
lbutton at the other key calling station may be as
removing the hold condition previously placed on ‘
station in the same manner as is the key-button '
which, when operated, would cause the associated
register relays to operate in a particular combina
tion to effect the operation of relay CT. Any one
of the key-buttons other than the No. 15 key
signed vto the key calling station A, the No. 15
key~button being ‘reserved for connections estab
lished over the two-way private branch exchange
line circuit associated with the other keycalling
\the connection by the operation of hold keyHA.
Incoming ‘call to‘lcey calling station ‘
All calls incoming to the key calling station
No. 15 at station A reserved.
When a call to station A is initiated at the‘
other key calling station relay CT operates in the
manner indicated above and at its ?rst armature
and front contact extends battery potential over
the sleeve conductor 43L thence over the lower
arrive by way of the two-way privatebranch ex
change line 2LX employed in the description“ just
made of a call originated at the key calling sta
tion by the actuation of the No. 15 key-button.
armature and back contact ‘of relay PB to ground
through the winding of relay SL’. Relay SL’ in
When this, line is, seized either by the operator ‘at
a manual exchange or'by the party at another key .
calling station, battery potential is applied to the
sleeve conductor to cause the operation of relay
S and relay SL’, the latter causing relay GT2 to
operating under this condition performs the same
functions ascribed thereto in extending a. call to
station‘ A under the heading “Incoming call to key _
calling station.”
' ~,
It will be observed that on a call to stationA
operate. The operating circuit for relay CT2 ex
which originated at another key calling station
tends from grounded battery, winding, of relay _
relay COL also operates. The operating circuit
GT2, conductor M6, ?rst ‘upper armature and
for relay COL extends from grounded ioattery,
resistance 240, upper armature and back contact
back contact of relay ICJ' (Fig. 2) , conductor 4H,
back contact and upper armature of relay'H2
(Fig. 4), third upper armature and front con~
tact of relay SL’, conductor “9,1 back contact
and second upper armature of relay L '(Fig. 2) to
ground- Relay GT2, atits ?fth upper armature
of relay S, winding of relay COL, front contact
and ?rst lower armature of relay SL’ to ground.
Relay COL, ‘in operating, connects battery by way
of its front contact and ?rst upper armature to
the sleeve terminal of jack JA by way of the
upper armature and back contact of relay PB thus
marking the line to the station A busy at the
and front contact, causes relay TK to operate in
a circuit previously described. At its second lower
armature and front contact relay GT2 completes 35 exchange.
the following operating circuit for. relay B (Fig.
3): grounded'battery, winding of relay .13, con
In a dial exchange a busy potential
would be extended to the connector multiple in
which the line of station A appears, to render the
line of station A busy to the automatic switches.
tact of relay GT2, conductor 4", back contact
Atits second upper and ?rst lower armatures re
and second lower armature of relay H2, second 40 lay COL opens the station A key calling line to
upper armature and front contact of relay‘SL' to
the private branch exchange thus providing a.
ductor “2, second lower armature and front. con
ground. Relay 0T2, operated, locks to ground
secrecy feature which precludes the attendantat
at the front-contact and first: upper armature of
the exchange from eavesdropping on such a con
relay B. Withrelays GT2 and TK operated, the
ringer III at the called station A is connected
directly across the tip and -ringconductors of the
nection. In this manner the line to station A is
not only marked busy at the exchange but the
transmission conductors are physically discon~
nected therefrom to thus render eavesdropping by
connection which 'now includes either the termi
nals of a connector switch at a dial exchange or,
as shown in the drawings, the terminals of jack
JA at a manual exchange.
In either case the
transmission of ringing current over the line is
effected in the usual manner to which the ringer
I l I at station A responds as a call signal. Trans
the attendant or operator impossible. '
Incoming call released ?rst by key calling party
In case the calling party‘ disconnects ?rst on an
incoming call relay SL’ will release and relay L2
will operate over the closed loop to the key call
mission battery is furnished by the private branch
ing station A by way of the back contacts and first
exchange equipment or by the other key calling
upper and second lower armatures of relay SL’.
equipment at the station at which the call is orig
The operation of relay L2 holds slow-to-release
COL operated, in a circuit extending from
When the calling party disconnects theattend
battery, resistance 440,7upper armature
ant removes the plug PA from jack JA and relay
‘SL’ releases its armatures causing the release of 80 and back contact of relay S, winding of relay
C‘OL, conductor 422, upper armature and front
relay B which releases, directly or indirectly, the
contact of relay L2, second lower armature and
relays GT2 and TK thereby restoring the circuit
front contact of relay COL to ground. When the
to normal. The holding feature described in con
handset llll is replaced on its mounting at sta
nection with a call originated at the key calling
station applies in the same manner to a call in 65 tion A relay L2 releases causing the release of all
‘ coming to the key calling station on the private
operated relays and restoring the circuit to nor
branch exchange line 2LX.
Direct station call
- Call incoming from another key‘ callingstatio'n
In making a direct station call. that is, a call
At the upper. right of Fig. 4 there is schemati 70
which is completed to a private branch extension
cally illustrated a single relay CT which is. identi
line ,by wayof equipment other than the regular
?ed as constituting a part of the equipment at an
private branch) equipment, the party‘ at the .key
other key calling station. The telephone set at
calling station removes the handset “H from its
such other station would be'furnished with a key
button assigned to the key calling station A 76 mounting and actuates the key button assigned '
to theueslred called station. . For descriptive pur
or relay FW,1b'ack contact‘ and upper armature or
poses it will be assumed that key No. 2 corre+
sponds to the desired private branchextension
line which is identi?edas line X2 on
7'. As
or relay L .to ‘ground.
shown on
relayrLOrpfront contact and ?rst lower ‘armature
Relay 10 now operatesin a circuit extending ‘
‘from grounded battery, winding of relay 10, com
5 this line corresponds to station ‘
ductor 226, front contactand third upper arma
ture of relay SW, conductor 2l2, to ground by
way of the ?fth upper armature ‘and front. eon-1
from its mounting the. sameirelays operate as pie‘
tact of connector relay "CTL Relay GT4 operated,
viously described-in connection with the exten+
‘sion of Ia-call' through-the ‘private branch ex; 10 locks ‘in 'a' circuit including grounded battery,
winding and from contact and ?rst ‘upper a'rma- '
change, and the register circuit comprising relays
til-re of'r'elay 0T4, conductor 500, ‘conductor 2M,
I, 2, 4 and 8 is connected through to the tip and
2X and terminates in jack U at the ‘exchange. ,
I When the handset IOl-at station A-is vretrieved
rront contact and ?rst upper armature "of relay
ring conductors T and R of the ‘calling line KC.
The party at station A then actuates the key but
fton No. 2 which causes relay2 of ‘the register cir
Band'ass'ociated ground.’
cult to operatelas indicated by the table shown‘
tact R2,which,"inliturn, connects recti?er 22l_to
to release. Relay-L at its second upper armature
in Fig, 7', I vlylore; particularly, the actuation of key
‘button No, 2 closes ‘the recti?er controlling con
the tip conductor 1‘ of ‘ line 'KC to callsethe trans
Relay 16 ‘at its second upper armature/opens
thetlockingucircuit for relayill. causing relay L
15 "
releases relay::C "and at ‘its llrst lowerarmature
‘opens the operating “circuit I'orrelay GT4. Relay
20 0 1at its glirst‘low'er armature releases register
relay 2 and at its secondupper and lower arma
tures connects the tip and ring ‘leads 2.02am 203
to the tripping ‘circuit. Relay 16 at its ?rst and
mission of an ‘impulse oyfapolarity such as to op-,
crate relay 52, over the tip conductor of’ the line.
_Register relay v2 operates in acircuitextending
fromgroundatstation .A, switchhook contact I02,
second lower armatures connects battery and
switchRA, recti?er controlling, contact‘ R2, nega 25 ground to the conductors oflline KC- through‘ the
windings of ‘relay A'.- Relay A" operates 'over the
‘tive poled recti?er 22, switchhook contact I05,
closedv'substation loop and applies ground to‘ the
winding of relay B to vholdwthis relay operated;
conductor 19$,tip conductor T of line KC, third
upper armature and back'contact of relay'IfK,
?rst" lower armature andfback' contact of’relay
10, second upper 'armatureandlront contact of
relay CO, conductor Bill;v negative po'ledrec'tig
?ers 3'23 and',324,‘lower winding of relay 2, to the
point '3?5and thence back to the grounded source
it will now be noted-thatjthesleeve'leadassoch
' P over the“ circuit traced 'hel'einbefore. ‘
IReglst'e'r, relay 2, operated, locks under control
of relay, 0 in the mannerpreviously described.
Rela'yl'FW operates 'in'thecircuit tracedfdr relay
before-break contacts} or-relayBY and the third
2 to‘wit'hhold "the connection of ground, at the
lower armature andifront cohtact'of relay L. ' The
front contact and ?rst lower‘ armature of relay L
sleeve lead of line X2 will have battery potential
‘tor-the ope'ratingvwindingol relay CT4iuntilthe
calling fpartlyat station A releases the No. '2 ‘key
button corresponding tothe‘ called station 2X.
When this 'key button is 'releasedprelay FW re‘
leases itslvarmatilre to apply?g'ro‘und potential to
the lead 334. “when this'occ’urs'relays',
and j '
GT4 operate. Relay S'Wope‘ratesin a cheaper,
tendingfrom grounded battery, winding and nor
- inal make-before-break“ contacts of relay f'SW,
conductor 230, back contact ‘and second lower
armature of register relay 8, contact 339 of rege
ister relay 2, conductori?, back contact and
armature of relay FW, back contact and upper
armature of relay 10, front contact and ?rst
ated with the "substation 2X-_,isjconnected byway
of the Irq‘nt'contact'and third lower armature of
relay GT4 to the leadg228 w‘monwhen relay ‘L
is operated extendsto‘ ground through the wind
'ing of '_~frela'y BY bywayor'the normal make
connected thereto Y n the station 2X ‘associated
therewith ‘is lousy, Under anassumed busy condi
tiontherero-re, relaygBYoperates. At its first
and second lower’ ati'natu‘r'é's‘, relay BY keepsthe
ringnconductor's open'to the [called stag
m1: ‘since. the Qperating‘oircmt for relay, BY
includes an armatureand-rroritcontact or ‘slow;
to~release 'relayn ‘it 'is apparent that the busy I,
test Of'the called line-‘is made‘ during therelease
sumed» busy condition iofthe‘ealléd line X2 to
station 2X, sends‘ busy tone back ‘to the calling ‘
station one locksuhdei‘ oonaoior relay
, The
path for the busy tone‘ current'extends from the
lower armature of ‘relay’ L toground'. ' It will be
tone supply TS (Fig; 2), conductor 233; condenser ' ’
observed at this‘ time that relay SW operates 55 231, front contact’ and's'eoond ‘upper annature of
only whenlegistenrelety' B is unoperated and
I relay ‘BY,’ 'conductor'235, front-contact and second
only when ‘one of ‘the register relays l, 2 or I»
lowerv armature of relay IC-,;=hack contact and seo- 1
is operated. Since, as indicated by the table in ' end lower armature of relay
ring conductor
Fig. <7, register relay -'8 ‘is operatedo‘nly on the
R. of line KC’, ‘through the closed loop’ at: Station
actuation of key buttons 8 to 15 inc'llusive,v the 60 A, tip conductor T or line'KC, third rupper'earma-l
relay SW operates only when one‘ of the key but
t'ur'e and-back contact'lof ‘relay'IfK, ?rstlower
tons 1 to 7 inclusive is actuated; By virtue of this
armatureand‘ frontcontact or relay It} to ground
arrangement ?fteen station selections’ may be
made by means of'only ‘eight connector relays
such as GT2, GT4, etc, one selection being enact
ed by each of the sets of upper and lower arose-l
cures ofthe‘ connector relays.’ I Connector relay
through the-upper winding of relay A’; ,Thls'ou'm
rent generates a‘ tone‘ signal in the‘ ‘receiver of
‘thelha'nds'et ml at station A, Upon-hearing ‘the
busy toue'sighal-in the receiver ofl'the vvhamlsset,
theparty at station Awouldlaball'don the'ca-ll by,
0T4 operates in a ‘circuit extending-from ground‘
replacing the handset-cults mounting ‘whereupon
ed battery, winding and normal make-before‘
the circuit is ‘restored to; normal; The‘ ‘release or ‘
break'contacts of- relay 0T4, conductor L2, front 70 thecirolllt results from the release of relay A'
contact'and fourth lower armature of ‘register
which, when relay 11c; operated was connected
relay 2, contact 34 l of register relay I, contact 340
directly acrossthe' callih'gend of the‘ connection
of register relay 4, conductor "232; fourth lower
armature and front contact of ‘relay SW, 'conduci
and whl‘cmat its armature‘and front-contact
established an obvious‘ operating ‘circuit {or slows‘
'tor‘23l, conductorst?; back contact "and armature 75 to~releaserelay B. Relay lei-releases relay ‘GT4, '
When' relay BY operated it locked to battery at
from conductor 304 which extends to the register
the third lower armature, and front contact of
relay IG and when the call is abandoned relay IG
restores its armatures to release relay BY thereby
discontinuing the tone signal.
The line X2 is marked busy at the exchange
by virtue of a battery connection to the sleeve
conductor thereof. This battery extends from
the back contact and ?rst upper armaturev of re
lay BY, back contact and third lower armature of
C'aflled Zine idle
When relay IC operates as described above it
relay L, third lower armature and front contact of
opens, at its ?rst upper armature and backcon
relay SW, conductor 228, and the third lower
tact the circuit to connector relay C'I‘Zwhich cir 10 armature and front contact of relay GT4.
cuit is e?ective in operating relay GT2 on calls in
Called station answers
coming to station A, thereby preventing double
connections- If the line X2 'to the called station
2X is idle, as is now assumed, relay GO releases
When the party at the called station 2X re
sponds to the incoming call signal, the tripping
due to the release of . relay C which relay released
when relayL released as above described.
relay C was operated, sloW-to-release relay PR
.was operated in an-obvious circuit, and when relay
G restores its armatures relay GO releases and
opens the operating circuit to relay PR. Relay
PR, however, remains operated for a short inter
val of time due to its slow-to-release character
istic. With relay CO released and relay PR op
erated, a circuit is completed from the grounded
continuous ringing supply GS, front contact and
armature of relay‘ PR,‘ normally closed make-be
fore-break. contacts of relay CO, conductor 238,
lower winding of tripping relay TR, back contact
and ?rst lower armature of relay TR, conductor
234, back contact and-second lower armature of 30
relay BY, second lower armatureand back con
tact of relay G, conductor 203, back contact and
secondupper armature of relay TK, conductor
relay TR operates ina well-known manner due to
the closure of the station loop circuit at station
2X. Relay TR disconnects the machine ringing
current supply from the called line and at its con
tact 244, and its‘front-contact and ?rst lower
armature connects the windings of relay D to the
called station 2X. Transmission battery is sup
plied to the called station through the windings
of relay D. Transmission battery is supplied to
the calling station A by way of the windings of
relay A’. The condensers 250 and 25l serve to
couple‘ the calling and called ends of the speech
transmission path extending between the calling
station A and the called station 2X. Conversa
tion between the parties at the two intercon
nected stations may now be carried on. Relay
TR locks operated under control of relay B,
When the handset at station A is replaced on
its mounting at the termination of conversation,
A releases due to the opening of the substa
contact of relay SW, conductor 240, second lower 35 relay
at station A and causes the release of
armature and front contact of connector relay
relay B. Relay B, released, causes relay GT4 to
GT4, through theringer circuit at'station 2X,
release'by removing ground from conductor 20!
front contact and ?rstlower armature of relay
served to hold relay GT4 locked operated.
GT4, conductor 422, front contact and second up
At its ?rst upper armature relay B removes
per armature of relay SW, conductor 202,‘ back
ground from the locking circuit to relay TR
contact and second upper armature of relay G,
whereupon relay TR releases. Relay GT4 at its
?rst lower armature and back contact ‘of relay
?fth upper armature opens the operating circuit
BY,.contact 242 of relay TR, ‘front contact and
to relay IG causing this relay to release. Relay
fourth‘ lower armature of relay 10 to ringing
ground. Thus the signal at station 2X,,is ener 45 B in removing ground from the conductor 20! also
2“! of link ‘KL, ?rst lower armature and front
causes relay PB in the private branch exchange
two-way line circuit 2LX to release and opens the
locking circuit of relay SW. The circuit is thus
gized in a continuous manner so long as relay PR
remainsoperated and immediately upon seizure
of the linev X2 by connector relay GT4. The sta
restored to normal.
tion 2Xv therefore is signaled immediately upon
seizure of its line, when idle, thereby overcoming 50 Call from secretcry’s station via private branch
the delay in transmitting a call signal by means
of machine ringing should the line seizure occur
during the silent interval between rings.
When relay PR releases its armature after the
time interval following the release of relay CO,
machine ringing from the source PS traverses the
path just traced for the continuous ringing cur
rent. Thelcalled station is therefore signaled in
termittently after having been signaled continu
ously for an interval of time corresponding to
the release time of relay PR.
The secretary’s station is, as shown on the
lower portion of Fig. 1, equipped with a telephone
handset I20 and associated induction coil I22, a
dial I2 I, a series of keys Kl, K2 and K3, a hold
key HE. and a call key GK. Incoming to the sec- .
retary‘s position are a plurality of lines such as
The signaling of
the called station is indicated to the calling party
at station A since the signaling current from the
line SL which is the secretary’s own private
branch exchange line, and line SLI. The pur
pose of the various keys at station S has been
hereinbefore indicated.
, When the secretary at station S desires to make
a call to a subscriber by way of theprivate
source PS is projected over the calling end of the
connection by Way of the back contact and sec
branch equipment at the local exchange, the
ond lower armature of relay TR, condenser 210,
back contact and second upper armatureof relay
key Kl is actuated, the latter‘ operation serving
handset I203 is removed from its support and
to connect the telephone at station S to the sec
retary’s private branch exchange line SL which
source TS. Relay GO released, opens the connec 70 terminates, as shown in Fig. 5, in the jack JS
at the, exchange. When the handset is removed
tion’between the'power source ;P and the register
from its mounting and key KI is operated, the
relays l, 2, 4 and 8. This is accomplished by the
line relay associated with the line SL and located
upper and lower fourth armatures of relay G0
BY, conductor 235 and thence over the same cir
cuit traversed by the busy tone current from
at the exchange is operated to bring in a call
which, when the relay releases, disconnect con~
ductor 302 extending from the. power source P
signal in the well-known. mannen. sheuld the.
secretary's. line
terminate, in. .a dial exchange
the keyv K2 is. actuated .to-connect her telephone
the call would be extended. tozthe called ‘station
set across the. line KC, and the call. key CKis
in the usual manner when-‘the dial I2I at station
operated‘ The latter operation connects'ground
potential to both; the tip and ring?conductors of
the line KC which, in‘ effect», isthe ecfuivalent of
operating the'No. 15 key button at the key calling
station A. -~Thus, whentthertelephone'rset‘at staa
. Sis actuated.
However, yin-the illustrated em~
bodiment of the inventionthe line SL. terminates
at the manual exchange P,.B. X. and the call
would‘ be vfurther‘extended vby the operator at the
exchange who responds to the call-.signala‘ssoci
ated with. the line Sh:
' Incoming call’;
~ "
tionS-is cénnectediacross the lineKC and the
handset removed from its‘ mounting, the register
' a
secretary .
'' Onan incoming call on line :SL theringer
would beactuated in the. well-known. manner to
indicate the arrival of a calllon the secretary’s
line SI). Upon receipt of suchs-a signallthe secre
'.HoZdind callon'ysecretarfs‘Zine
_ I'
When a connection is completed to. thesecre
tary’s station Sby wayof line SL, the call may
be held by the secretary byv the actuation of. hold
operate'in ‘response to the‘actuation of call key
CK at station S in the same vmanner as described
in connection-withithe ‘origination of a callat
station‘ A by‘theactuatlon' of-lkey button No. 15.‘
The register relays I,/2-;14'and.8 function to oper
ate relay GT2 which connects thelin‘e‘KC-to the
two-way; private branch‘ exchangev line '21.)! .in
tary would actuate the. key KI‘ associated with
theline corresponding to-ringer I24 and‘ remove
the'telepho'ne- handset,v I20. from itsmounting.‘
circuit, including relays I, 2;,4 and-i8, is connected
to thelinaKC and register. relays I, izyl-and 8
. the manner previouslydescribed.v ‘In this‘ inan
20 ner thesecre'tar'y not only has access to'regular
private vbranchiie'xcha'nge'service by way ‘of, the
line SL butial’so byway of the line KC. *' The oper
ation of- theCTZrelay- serves ‘to bring in a lamp,
key HK. When-the‘connection' is'established,
relay. I25, whose windi'ngis includedlin onewof
signa'lin the case of a manual‘ exchangeor to I
start theline ‘?nder functioning-inv the case'vof
the line conductors of ,the line SL ‘operates over '
adial exchange "in'the mannerdescribed in 'con-‘
the closed loop at-the secretary's station from
battery at the exchange. Theopera-tion- ofirelay
nection with theope'ration of the No.1}; key'but
ton at 1station*S.*-"‘
I25 at this time performsno useful function‘ To
‘ "The secretary may'place ahold condition on a
hold the connection'the. hold key HK ‘is actuated '
connection originated by ‘her vover the line ‘KC, ‘
which results ,inithe. opening of one side‘ of the
In thiscase‘the hold vkey HK is actuated which ‘
line SL to the secretarystelephone thus causing
opens vthe tipcon'duetorl to the station vS and
the release of relay I25. ‘A circuit is‘now closed
connects it" to the ‘ hold lead which includes the
from‘ the exchange, over the tip- conductor 254
windings of ‘relay vI3I so that relay I “operates
of line SL,'top winding of relay. I26, outer left a1= ‘
overt-he closed loop at ‘station S,v the operating
battery'being'iurnished at the exchange. Rel
lay rarm- operating, applies‘ground to the tip
ternate contactsof key KI, make contacts‘ of hold
key vHK through theclosed loop at the station
S, middle alternate contacts of key KI, and back
to the exchange by way of the :ring conductor 255
ofline SL;
I -' ‘-
conductor‘ of line‘ KC_'t_O_' cause an unbalance, in
the'line'current" traversing the windings of dif
Relay I25 operates in this circuit tovconnect'a
holding bridge acrossthe'tip and ring conductors
of the line-SL.» -More particularly, this holding ‘
circuit includes the armature and‘fr'ont contact
offrelay I 26, bottom winding of ‘relay I26 and
thenon-inductive _.winding* I 28;- This bridge I
held ~in this‘ manner, 'itjmay be picked up either ~
by the secretary or by the party at theykeyj'calli'ng
llrgmsf'e?ring call from
‘v ‘key calling ,¢
station to
fu'nctionsto hold the'established connection on
line SL- so that the secretary may perform'oth'er
.When- the party at the'key calling ‘station ‘A
duties-,such, for'e'xample, as answering an‘ in
wishes the secretary at station ‘S ‘to pick vup‘ a call
coming call‘ on line SLI "by ‘actuating key 1K3‘ as
' soeiated therewith.
ferential relay DF,;causing this relay to ‘operate
to-put-aholdcondition'on the line in the manner
previously-described; When the connection‘ is
which-the former has originated iorlreceived-on'
The arrangement of keys
line KC, the secretary is so advised and her tele
phone isiconnected in multiple with the key call
KII,‘ K2, K3 and key HK is such thatwhen-the
hold ‘key HK 'is operated; the key‘ KI, which was
operated when the call onl'line SL'waslofriginally
completed; is automatically‘, restored. vThe resi
to'rati'o'n of key KI causes the opening of the
original energizing circuit‘ for relay I26 by way
of it's ‘top winding; The relay I26: is-now'held
operated over the'tipand‘ring conductors of line
SL byway of its bottom‘winding'a'n‘d its "non
ing v‘station ‘by the‘ actuation, of’ keyv K2, ' and‘ the
handset1I20Tis'».removed"from its mounting." If
the call'came in over the private branch'exchange
equipment-,a hold condition may. have been put '
on the line before the-secretary was-toldv to pick
upvthev call. In this case the secretary operates‘
the call-key CK which, as hereinbefore indicated,
produces ‘the same results in theregister circuit
as. key 'No. ‘15 at the key calling‘stationyA." iThe
To again pick up the connection on line SL;
the secretary at stations merely actuates the key
to the. two-way. private branch exchang'eline ZLX Y
inductive winding‘ I28; and*~the station equip-v
ment' is disassociated from the line SL."
“ -
KI to ‘automatically associate the telephone ‘set
[20"With the line SL which causes‘relay 125 to
reoperate. At itsj'front contact‘ and-armature‘
relay I25 short-circuits the bottom'winding of
relay ' I26 'thereby‘causing relay I26 ‘to release‘
which removes the holding bridge from the line
and restores 'the‘ycircuit to vthe talking condition.v
Coll lay-secretary over the feet culling}stationv line
Should the secretary ‘at-stationv S- desire to‘
make a-call-over the keylcalling stationiine'KC,
circuits‘then functionyto establishla connection
which‘removes the hold condition and permits
the secretary to talk on the connection.“ The
manner inewhich thehold condition ‘is’ removed- -
when the secretary ‘operates the-call key. CK is
thesame when the hold condition is removed on
a, connection again picked up by the party at the
key; calling stationyA'in operating key button No.‘
115 as previously described under the heading
"fHolding by key callingrsubscvriber.”
‘ : ' v-C'aZl‘from key'cdll'ingstation'to secretary‘
“When-Whe- party at the key ‘cam-11g amt
wishes to talk to the secretary by telephone, the
call is started by removing the handset IIII from
its mounting atstation A and by operating the
key button assigned to the secretary’s line which
PS. The ringing signal path may be traced from
the grounded continuous ringing current source
CS, front contact and armature of slow-to-re
lease relay PR, normal make-before-break con
in the present disclosure is key button No, 1. 5 tacts of relay CO, conductor 238, lower winding
When the handset at station A is removed from
and back contact and ?rst lower armature of
its mounting, the line KC is extended to the
tripping relay TR, conductor 234, back contact
register circuit in the same manner described
and second lower armature of relay BY, second
hereinbefore. The operation of key button No. l
lower armature and back contact of relay C, con
as indicated by the table of Fig. '7 causes recti?er 10 ductor 203, back contact and second upper arma- '
controlling switch RI of the key calling station
key-set to be closed and to connect recti?er I I to
the tip conductor of the line KC, whereupon a
circuit is completed which may be traced from
ground, switchhook contact I021, switch RA, rec
ti?er controlling switch RI, positive poled recti
?er II,v switchhook contact I05, conductor I05,
tip conductor T of line KC, third upper armature
and back contact of relay 'I'K, ?rst lower arma
ture and back contact'of relay IC, second upper
armature and front contact of relay CO, conduc
tor 3M, lower winding of register relay I, posi
tive poled recti?ers ,3 I8 and 3I9, to the point 305,
positive poled recti?er 32I, winding of relay F'W,
positive poled recti?er 322, conductor 304, front
contact and fourth lower armature of relay 00,
front contact and fourth upper armature of relay
CO, conductor 302, to ground through the alter
nating current source P. Relays I and FW op
erate in this circuit on the positive pulse resulting
from the actuation ofthe No. 1 key button at
station A. Relay I locks operated under control
of relay C in the manner previously described.
When the key button No. l at station IA is re
ture of relay TK, conductor 2I4 of link KL, ?rst
lower armature and front contact of relay SW,
conductor 240, second lower armature and front
contact of relay CT5, corresponding conductor
of the link SX, lower armature and back contact
of relay El, conductor 254 of the secretary’s line
SL, Winding of relay I25, operating coils of ringer
I 24 located at the secretary’s station S, conductor
255 of the line SL, winding of relay SY, back con
tact and ?rst upper armature of‘ relay El, front
contact and ?rst lower armature of relay GT5,
conductor 422, front contact and second upper
armature of relay SW, conductor 202, back con
tact and second upper armature of relay'C, ?rst
lower armature and back contact of relay BY,
contact 242 of relay TR, to ground by way of the
front contact and fourth lower armature of relay
IC. The ringer I24 at the secretary’s station S
responds in a continuous manner to the current
traversing the path- just traced. This continuous
signal persists just so long as relay PR. holds its
armature on its front contact and when» the ar
mature is released, the machine ringing source
PS is substituted for the continuous ringing
source CS to cause the secretary’s ringer to op
leased relay FW releases causing relays SW and
GT5 to operate. The operating circuit for relay
erate intermittently. The current from the ma
SW extends from grounded battery, winding and
chine ringing source PS traverses the same path
traversed by the continuous ringing current ex
normal make-before-break contacts of relay SW,
cept that it is supplied to this circuit by way of
conductor 230, back contact and second lower
armature of register relay 8, contact 342 of reg -40 the third upper armature and front contact of
relay IC and the back contact and armature of
ister relay I, conductor 334, back contact and ar
relay PR. Relay SY may operate on the ringing
mature of relay FW, ‘back contact andupper ar
current. The secretary’s line at the exchange
_ mature of relay LO, front contact and ?rst lower
armature of relay'L to ground. Relay GT5 (Fig.
is marked busy in the same manner that the line
5) operates in a circuit extending from grounded
X2 was marked busy as hereinbefore described.
battery, winding and normal make-before-break
When the secretary at station S responds to
contacts of relay GT5, conductor LI , back contact
and second lower armature of register relay 2,
contact 3'“ of register relay I, contact 340 of reg
ister relay 4, conductor 232, fourth lower arma
ture and front contact of relay SW, conductor
23I, conductor 334, back contact and armature of
relay FW, back contact and upper armature of
relay LO, front contact and ?rst lower armature
of relay L to ground. Relay 0T5 locks to ground ;
at the front contact and ?rst upper armature of
the operation of the signal and removes the
handset I20 from its mounting and actuates key
KI to pick up the line SL, the tripping relay TR
operates to connect battery and ground to the
called end of the connection by way of the wind
ings of relay D. When this occurs relays VSY and
I25 operate over the closed loop at the secre
tary’s position. Neither of these relays performs
any useful function at this time. Transmission
battery is furnished the secretary’s line from the
battery associated with relay D while transmis~
sion battery is furnished the key calling line KC
from the battery associated with the relay A’.
The. key calling station A is now connected for
communication to the secretary's station S and
conversation between the parties thereat may be
relay B by way of its ?rst upper armature and
front contact and conductors 500 and 2M. Relay
SW locks to thesame ground by way of its front
contact and ?rst upper armature and conductors (30
433 and 2!“. At its ?fth upper armature and
front contact relay CT5 connects ground to con
ductors 225 and 226 to cause relay IC to operate.
carried on.
Relay IC performs the same functions hereinbe
It will be observed that relay PB of the two
fore ascribed to it.
way private branch exchange line ZLX to the
The circuitsfunction to test the called line SL
key calling station is operated during direct sta
. and to apply signaling current thereto, if idle, in
tion to- station calls such as the call from station
the manner described hereinbefore in connection
A to the secretary’s station S, just described, and
with the testing and signaling of the extension
in operating busies the two-way line to the cen
station 2X on line X2. As in the case of the call
tral office equipment thus rendering the line in
extended to the extension station 2X, the called
accessible to such equipment when the key call
secretary’s station receives an immediate ringing
ing station line is in use. The operating circuit
signal from the continuous ringing current source
for relay PB includes the ?rst lower armature
CS which is followed by an intermittent ringing
and back contact of relay GT2.
signal originating at the machine ringing source 75
The circuit is restored to normal when the
interconnected parties ' restore 5 the'if‘handsets ‘ to"
of "relay. GT5,‘ 'conductor"L3,r front ' contact and
their; respective mountings.‘
first lower- armature of‘ relay], contacts 31! of
relay I,' contact 340 of relay 4, ?rst lower arma
ture‘ and front contact of relay 8,‘ conductor 334,
back-‘contact and armature of relay
_ _- "
I‘ : ~
'. . .' Call?held by secretarypickedtip.
[at key calling station
- .
' When the secretary has received acall over her
lineSL ‘and'wishes the. party atthe .key calling
station A'to pickup that call, the secretary-?rst,
contact and'upper armature of relay L0‘, front
contact and ?rst lower armature ‘of relay L to
. ground. 7 Relay SW does not operate at this
puts a hold‘ condition on the line'SLwhich dis‘- '
time since the‘ key button ‘actuated ishigher in
connects the station from’ the line and requests 10
the party at the key‘. calling station to pick- up w
the call.
Relay C'I‘B locks operated ina circuit‘e'xtend;
ing from grounded ‘battery, Winding’ and front‘
1It will be assumed that the'call‘incoining» to the
contact and ?rst upper armature'of relay'CTG;
secretary's station S 'by‘way" of the line-SI; orig’
conductor 500, conductor 20l,‘ and
inated at the manual exchange at which ‘the 15 ?rst upper armature of relay B to ground.‘ When
line'SL ‘terminatesin‘thejack'JS. It is to'be
relay-GT6 operates it completes an operating cir
understood that the call may just as well have
cuit for relay TK ‘which may he traced ‘:from
been. extended to the line SL by way of automatic
grounded battery,'winding oi‘relay TK, conductor
switching ‘equipment- at a dial exchange. " In
2 H, back contact ‘and third‘ upper armature'of
either case the ringer ‘[24 at the station S' is 20 relay SW,‘ conductor 2'l2,"?fth upper armature
actuated when sig'n'aling'curtent is applied‘toj the
line SL at the exchange. In' answer to-this signal,
the secretary actuates key Kl to connect‘ the
telephone equipment at station S to the'line SL
and front contact. of‘ relay'CTG ‘to ground. ‘ Relay
TK' operated, disassociates the tip and ring con
ductors T and R of the lineKC from the conduce
tors 300 and 30 Iv which extend to the register ciré
and then removes‘ "the ‘handset T 120 ‘from its 25 cuit, thereby disconnecting the register from the
mounting; In response to‘ these" operations,
calling line; Relay 'I'K'also opens the locking cir
relays I25 and SY'ope'rate and perform no use
cuit -fo'r relay L causing this relay to restore its
tul functions at, this time. slow-release relay SR
armatures. Relay B, however, does not‘ release as
operates-as a consequence of ‘the operation ‘of
it is now held'operated in a circuit controlled by
relay SY for a purpose to be hereinafter explained 30 the second upper armature and front contact of
in detail. ‘It willbe- noted, however,‘ that the
relay El in the secretary's line circuit BL as ‘will
operating circuit for relay SR‘ includes the back
contact and second upper armature ‘of relay El.
Relay TK vat its third ‘upper’ and ‘?rst ‘lower
appear presently.
' Since the call which the secretary haslan
swered is to be picked‘up by the‘ party at the key
calling station A, the secretaryope'ratesthe hold
key HK which releases the Kl-key‘which discon
meets her telephone set from the line-and then
requests the party at station A to pick up the‘ held
call. '
the hold
_ l-IK is operat'eclli,v
_ here‘ 40
inbefore’described, relay I25 releases and relay I26 ‘
'operates, the latter 't'o'effectively connect-the bot‘
tom winding and the ‘non-inductive winding ' I28
armatures and associated front contacts‘extend's
the tip conduct-or T of the line KC‘ to the lower
winding ‘of relay DF and at its second lower and .
?rst upper armatures and associated‘ frontf'cong
tacts extends the‘ ring conductor R-of the‘line KC
to the upper winding or relay'DF vso that, with the
subscriber’s loop'closed at station A by virtue of
the" handset thereat being‘ removed _from -_its
mounting, relay. E of the ‘secretary’s'line circuit
SL operates from the exchange battery, ‘which; on
of relay-‘I26 across theline 'as a holding bridge.
the connection to’ the’se'cretary’s ‘station how
‘Thus the call on line-5L is held; When thepart'y 4,5 held, supplied the battery to the‘ secretary’s tele- '
at station A is advised to pick up the call/‘the
key button‘ at station A assigned dfor this {purpose
is‘ actuated after‘ the handset 101 is “removed
from its mounting? The key button No. 11 is vasl
phone. ‘The operating ‘circuit for‘ relay E maybe
‘traced from one te'r'minal “of the exchange battery
to the ring'te‘rmin'al of jack ‘JS by Way of which
the "connection "was extended. to the secretary’s
sumed‘to'have been‘ assigned for this purpose and 50 line SL, winding-of 'relayiEhfront cont'act'a'n‘d!
this key button is accordingly actuated. ' ‘.It‘is un
necessary to ‘repeat the'description of the‘relay
Operations “resulting ‘from the removal of 'the
‘handset WI at station A'frorn itsr‘hands‘et- ‘since
third ‘upper armature of relay CTB, conductor‘l?i,
ba'c'k *conta'ctand ?rstlower ‘armature of relay
SW, conductor 2l4'of the‘ link KL, 'back contact
and second upperw'ar'mature of relay HR, upper
. they have-been‘ Tully-set f'orthl hereinbefor‘e? -
When the N0. 11- key ‘button is actuated," the
recti?er-control switches RI; R2 and R8’ are
closed as ‘indicated by the ‘table shown‘in Fig. "7.
The‘ closure of switches RI , R2 and R8 res'ultsinv
armature and‘ front ‘contact ‘of relay TK, front
contact ‘and second lowerarmature ofrelay TK,
' as akeyilautto'n at ‘station ‘Ais operatedi Relay
{IS and thence to the other- terminalv of "the ek~
ring conductor R of line KC, through the closed
subscriber’s loop at station 'A; tip‘ conductor'l‘ of
the operation of register relays “I”, 2 and B.‘ The .00 line KC,- third upper ari'naturehnd front contact
‘circuits in which these relays operate "haye been
of relay 'I'K, front contact and ?rst lower armaé
traced _'hereinbe'fore in - connection"with - the
ture of relay ‘TK, lower winding of differential
actuation of key ‘buttonNo; 15 and ‘need ‘not be
relay‘DF, ‘?rst upper, armature and back contact
‘repeated. It has alsobeen ‘hereinbefore described
of relay HRQconductor 2'l6 of link KL, second
‘how these ‘register relaysflock, when operated, 05 upper
armature and backcont'act‘of ‘relayUSW,
under control'oi r'elayiC. It has scopes-n‘ de
conductor- I06, fourth upper'armature and front.
scribed ‘how relay 'FW remains‘ "operated?so' long
contact of relay CTB, to the tip terminal-‘inf jack
'FW restores its armature when the ‘key '-button"_'is
change battery (not shown). Relay E operated.
released to complete ‘an op'erating (‘:ircn‘it‘v for ‘the 70 establishes an obvious operating, circuit fora-relay
‘connector r'elayi corresponding "to the particular
El. Relay El ,vat ‘its second vupper armature-and
register relay ‘or relays opera-ted.‘ .'
reiays" i,
contactv completes the ho'lding'circuit for
v2 and! operateduconnector relay C'lfB operates ffron't
relay ‘B. above referred to, by connecting ground
in a "circuit extending from‘ grounded battery,
winding and normal make-beforeefbreak contacts;
trithe _ front vcontact and ?fth. lower armature of ,
“relay 0T6‘, conductor 1H2,v winding of relay ‘B to
battery and ground. Thus relay B is held oper
ated to maintain the supervisory circuit in the
cut-through condition.
With relays 0T6 and TK operated, the key call
ing line KC is extended to the multiple extension
line is seized in the same manner as areother
lines such as the two-way private branch ex
change line circuit 2LX or a line extending to
one of the frequently called stations. More par
ticularly, a call to the exchange over line LX
SXl of the secretary’s line SL and is therefor now
connected to the calling end of the connection es
is initiated at station A by the removal of the
handset l0! from its mounting and by the actu
ation of a key button assigned to the line LX. In
tablished tovthe secretary’s line ‘SL. It remains
the present disclosure a connection between the‘
now to be described how the hold condition placed
on the line by the secretary is removed. This hold 10 key calling station line KC and the one-way
branch exchange line LX is completed when key
condition, as hereinbefore described is e?ected by
button No. 10 at the station A is actuated after
the holding bridge comprising the bottom winding
the removal of the handset [M from its mount
of relay I26 and non-inductive winding l28
ing. It is believed unnecessary to describe the
which were connected across the conductors 254
operation of the supervisory equipment (Fig. 2)
and 255 of the line SL when the hold key HK was
incident to the removal of the handset l lll from
operated. This holding bridge is the means by
its mounting since this description has been made
which relay SY is operated. When relay El oper
previously in connection with a call extended by
ated due to the operation of relay E as above de
way of the two-way private branch exchange line
scribed, the operating circuit for slow-to-release
relay SR is opened. This relay, due to its slow .. 2LX.
When the key button No. 10 is actuated at sta
releasing characteristic holds operated for an in
tion A, recti?er control switches R2 and R8 are
terval after the operation of relay El. At its ?rst
closed to effectively connect the recti?ers 22 and
upper and its lower armatures, relay El opens the
88 to the tip and ring conductors T and R, re--.
lineconductors of the secretary's line SL towards
the secretary's station S. These line conductors ! - spectively of the line KC. As shown in the table
of Fig. '7 register relays 2 and 8-operate in re
are alsov opened at the armatures of relay SR
sponse to the actuation of key button No. 10. It
until relay SR restores them to reestablish the
is believed unnecessary to trace the operating
continuityv of the line conductors. Thus, for an
circuits for relays 2 and B of the register circuit
interval correspending substantially to the re
at this time since they have been describedin
lease time of relay SR the secretary’s line SL is
detail hereinbefore. Su?ice it to say that when
disassociated from its jack terminals so that the
these relays operate, they look operated under
exchange battery is disconnected from the line
the control of relay C and establish an operating
SL causing relay l26 to restore. The restoration
circuit for connector relay GT4. Relay GT4 oper
of relay I26 removes the holding bridge from the
line SL in the manner previously described. When ~ . ates in a circuit extending from grounded bat
tery, winding and normal make-before-break
relay SR eventually releases its armatures, the
contacts of relay GT4, conductor L2, front contact
line SL is again extended to the terminals of Jacks
and fourth lower armature of register relay 2,
JS at the exchange. The party at the key call
normal contact 34l of register relay l, normal
ing station may now converse with the party on
the calling end of the connection.
40 contact 340 of register relay 4, ?rst lower arma
ture and front contact of register relay 8,'con
The connection just described is released in
ductor 334, back contact and armature of relay
substantially the same manner as the connection
FW (relay FW releases when .the No. 10 key
involving the two-way private branch exchange
line hereinbefore described. This connection may
be picked up again (prior to its release) by the
secretary if such action is required. If theparty
at the key calling station wishes to transfer the
call back to the secretary, the secretary is told
verbally to pick up the call. When the secretary
picks up the line SL by actuating the key KI and =
removing the handset 120 from its mounting. re‘
lay 'SY operates from the exchange battery over
the closed loop at station S and when the party'at
button at station A is restored), back contact
and upper armature of relay LO, front contact
and ?rst lower armature of relay L. Relay GT4
_ locks in a circuit extending from grounded bat
tery, winding and front contact ‘and ?rst upper
armature of relay GT4, conductors 400 arid 2M,
to ground at the front contact and ?rst upper
armature of relay B. Relay TK now operates in
a circuit from grounded battery, winding of rel
lay TK, conductor 2“, back contact and third
upper armature of relay SW, conductor 2l2, to
the key calling party station disconnects, relay E
releases causing the release of relay El and the“ ~' ground by way of the ?fth upper armature and
front contact of relay GT4. .
operation of relay SR. Relay El at its second up
Relay SV in the one-way private branch ex
per armature removes ground from the winding of
change line LX now operates in a, circuit extend
relay B in the supervisory circuit causing this re
ing from grounded battery, resistance 251, back
lay to restore its armatures. Relay B opens the
contact and ?rst lower armature of relay SLX,
locking circuit for relay 0T6 which releases its
front contact and third upper armature of relay
armatures thereby opening the operating circuit
0T4, conductor 405, back contact and ?rst lower
for relay TK and releasing the multiple extension
. armature of relay SW, conductor 2 l4 of link KL,
SXl of the line SL. Thus the connection estab
back contact and second upper armature of relay
lished by the party at the'key calling station is
HR, upper winding of differential relay DF, ?rst
released when the connection is picked up by the '
upper armature and front'contact of relay TK,
secretary and the party at the key calling station
front contact and second lower armature of re
Outgoing call by way of one-way private branch
exchange line
I When it is found desirable to furnish a key
calling station with more than one line to the
private branch exchange a one-way line circuit
such as indicated at LX (Fig. 5) maybe provided.
This line is used for outgoing service only. This
lay TK, ring conductor R of line KC. through -
the closed loop at station A.-tip conductor T of
the line KC, third upper armature and front con
tact of relay TK, front contact and ?rst lower
armature of relay TK, lower winding of di?'eren
tial relay DF, ?rst upper armature and back con
tact of relay HR, conductor‘ 2“? of link KL, sec
ond upper armature and back contact of relaxr
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