Патент USA US2606982

2,606,976
Patented Aug. 12, 1952
UNITED STATES ‘PATENT OFFICE *
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2,606,976
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_ INTERCOMMUNIGATING APPARATUS
Richard H. Campbell, Racine, Wis., assignor to
Webster Electric Company, Racine, Wis., a cor- ‘
poration of Delaware
Application March 26, 1948, Serial No. 17,155
13 Claims.
(01. 179-1)
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1
The present invention relates to intercommu
nicating apparatus and has for its primary ob-'
ject the provision of. new and improved apparatus
so constructed and arranged that the remote sta- '
of this character and‘ a system including such
tions 2 and 3 can call the master station and that
the master station can call the remote stations
and control the direction of communication be
apparatus.
tween the stations».
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The master station includes an ampli?er l0
comprising an input transformer 12 and an out
put transformer l4 interconnected by tubes 16
‘spe‘aking intercommunicating system utilizing
and [8, which may be of known type and con
but few interstation conductors andcircuit con
trolling'switches andv which is substantially bal 10 nected in known manner. Power jis‘supplied to
the ampli?er from either an A. C. or D. C. source
anced so Ias‘to eliminate hum and, more particu
through rectifying means including a tube 20.
larly, to. provide a system characterized by an
The three stations illustrated are each pro
ungrounded com'monconductor and amplifying
vided with electroacoustical translating means
means having reduced feedback from the output
15 which may be loud-speakers 2 I, 22' and 23 located
to the input.
at stations I, 2V and 3, respectively. The master
A further object of the present invention is
station is also provided with a Communication
the provision of an intercommunicating system
One of the objects of the present invention is
to provide a new, improved, and simpli?ed loud
direction and ampli?erpower supply controlling
including at least one master station, a station in
switch, indicated as a whole by reference char
cluding electroacoustical translating means, Iain
plifying means and a selectively operable com— 20 Iacter 24. It is also provided with station selector
switch means 125 and the remote stations are ‘pro
munication control switch, and one or more other _
stations, each including electroacoustioal trans
lating means, andwherein each of the latter sta
vided with call-in switcheS 25C.
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The \ communication direction and ampli?er
power. supply controlling switch 24 is operable
tions may call the master station, even when
the latter is communicating with another of the 25 into a plurality of ‘positions. ' These are ‘a listen
said other stations.
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A further object‘ of the present invention is the
provision of .new and improved‘ communicating
apparatus comprising a plural position communi
cation control switch'and visual‘ means adapted
to indicatedi?erent positions of. the switch.
Another-object of "the present invention is the
provision of new and ‘improved intercommunicat
ing ~=apparatus adapted to be supplied with power
position, in which the switch is indicated, a talk
position, ‘which is one position downwardly from
that indicated, and an idle position. ‘which-is one
position upwardly from that indicated. In the
idle position, the supply of plate voltage from‘ the
recti?er to the ampli?er is discontinued but
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the other-two positions the ampli?er issupplied
with plate voltage and is Operative. In the listen
position, the loud-speaker 2i is connected to the
through a recti?er having resistance means at its 35 output of the ampli?er,‘ while a. communication
circuit comprising conductors 26 and 28, the lat
input side for supplying added ?lter action, act
ing as “a fuse under certain conditions and as a
ter of which is, in accordance-With one of the
peak charging current'lhniter and, still further,
features of the present vinvention,
cooperating with resistance means controlled by
a multiple position communication control switch
to provide a reduced-‘output voltage in certain
the ampli?er input and output, is connected to
the input of the ampli?er. The connection to the
‘positions of the switch. I
output > of ‘the amplifying
I
Other objects and‘advantages .of the present
ungrounded
common conductor for the loud-Smkersand for
means ' is effected
through'a secondary» winding 30 of the output
transformer- l4, while the connection to the input
invention will becomeiapparent‘ from the .en
suing description of ‘an embodimentxthereof, in 45 is effected through the primary winding 32 of the
the course of which reference is had .to the ac
companying drawing, thesingle‘?gure ofswhich
is ‘a schematic representation of .annapparatus and
input transformer l2.
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‘The u'seof an ungrounded-commonlme
,
the
advantage that the number of contacts on‘ the
communication direction control switch 24 can be
Referring now. to the drawing, the present in 50 reduced, as only one side of the communication
circuit .hasto be switched,v and yet the communi
vention is illustrated in connection with a system
cation circuitis substantially balanced with the
including "a .?rst station, indicated by ‘the refer
result‘that crossetalk, noise and hum are mini
ence character l, which is a master station, and
system‘ embodying the invention.
two other stations 2 and-3,,located :atadistance '
from thef?rst stat-ion and which'will- hereinafter 55
be called remote zor: substations.‘ The system is
miZed.
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In the indicated listen position of the switch,
the loud-speaker 2| is connected to the secondary
2,606,976
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winding 38 of the output transformer and the
communication circuit 26, 28 is connected to the
primary winding 32 of the input transformer.
The connection of the loud-speaker to winding 38
is effected through the common conductor 28,
which connects one terminal of the transformer
to one terminal of the loud-speaker coil, and
through conductor 34, switch blades 36 and 38 of
switch 24, and conductor 40. The communication
circuit 26, 28 is connected to the input trans 10
former primary winding 32 through the common
conductor 28 and through conductor 42, switch
blade 44 of switch 24, and conductor 48.
In the talk position of switch 24, the connec
tions of the communication circuit 25, 28 and of 15
the loud-speaker 2| to the ampli?er are reversed.
The loud-speaker is connected to the input of the
ampli?er through the previously mentioned con
ductor 28, conductor 48, switch blades 36 and 88,
and conductor 48. The communication circuit is
connected to the output of the amplifier through
the common conductor 28 and through conductor
42, switch blade 44, and conductor 34.
In order to minimize feedback from the output
to the input of the ampli?er, a resistor 48 is con 25
nected across the input and the secondary wind
ing 38 of the output transformer I4 is so phased
relative to the input that they are in phase op
position at higher frequencies passed by the
ampli?er. The resistor 48 loads the input trans
former and prevents a phase shift that could
result in feedback (oscillation) of the ampli?er.
The feedback is also reduced by a shield 50 be
tween the primary and secondary windings of the
input transformer and which is connected to 35
ground (the chassis of the unit) by conductor 52.
The resistor 48 also limits the primary impedance
and therefore minimizes noise and hum pickup
between interstation wires.
The station selector switch 25 is adapted se 40
lectively to connect the communication circuit 26,
28 to the remote stations 22 and 23. The selector
switch 25 includes two switch blades 56 and 58
connected, respectively, to conductors 26 and 28.
Each blade is operable to engage a plurality of 45
contacts which may be connected by interstation
conductors to the remote stations. In order to
simplify the present description, only the two
stations 2 and 3 have been illustrated. The
former is connected by conductors 68 and 82 to
corresponding contacts associated with switch
blades 56 and 58. Station 3 is similarly connected
by conductors 64 and 66 to the corresponding
contacts of the two switch blades. In the indi
cated position of the selector switch, station 3 is
shown selected, the switch blades 58 and 58 con
necting conductors26 and 28 to conductors 64
and 86, respectively.
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master station (and this is done when the switch.
24 at the master station is in its listen position) ,.
all that is necessary is the closure of the call-in
switch 250, thereby to connect the associated
loud-speaker to the call-in circuit and thence
to the input of the ampli?er as previously de
scribed.
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Other features of the present invention reside
in the control of the plate voltage supply and in
means for indicating the various positions of the
switch 24.
The communication direction and power sup
ply controlling switch 24 is constructed and ar
ranged to complete the plate voltage supplying
circuit to the recti?er 28 in the listen and talk
positions. The recti?er is conditioned to be ready
for operation as are the tubes [6 and i8 of the
ampli?er upon the completion of the recti?er
plate voltage supply circuit. The tubes 16 and
I8 are permanently connected to the output of
the recti?er and all three tubes have their ?la
ments connected in series across the power sup
ply by conductors 18 and 18. Thus, the ampli?er
is rendered operative whenever the plate voltage
connection to the recti?er is completed and this
connection is completed by switch blade 88 of
switch 24 in the listen and talk positions of the
latter. In the listen position, the recti?er plate
voltage circuit is completed through a pilot light
82, which serves a number of functions as will
be brought out hereinafter, resistor 84, conduc
tor 86, switch blade 80, resistor 88, and conductor
99.
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The resistor 84, in accordance with another
feature of the present invention, cooperates with
resistor 88 to provide a reduced plate voltage to
the ampli?er tubes in the listen position. The
resistor 84 is also designed to act as a fuse in the
case of short circuits and it also acts as a peak
charging current limiter whenever the recti?er
is placed into operation and prevents the pilot
light 84 from being supplied with too high a cur—
rent upon initial closure of the plate voltage cir
cuit. In the talk position of switch 24, the switch
blade 80 interconnects conductors 86 and 90 and
thus eliminates resistor 88 from the circuit so
that a higher plate voltage is supplied to the
recti?er and the latter thus supplies a higher
plate voltage to tubes 16 and Hi. The result is
transmission at a higher level than reception.
The pilot light 82 indicates the positions of
the switch 24. In the idle position of the switch,
a low value of current flows through the light,
the pilot light being connected from conductor
12 to the midpoint of the cathode heater or ?la
ment 92 of the recti?er tube 20 by a conductor
94. In the listen position of switch 24, a greater
current ?ows through the pilot light because
the plate current ?ows through it. At this time
In accordance with another‘ feature of the pres
ent invention, the remote stations can call the 60 resistors 84 and 88 are in circuit with the pilot
master station even though the selector switch 58
light so that a lower value of current flows
is left in position to select a particular station.
through it than when the switch 24 is in its talk
position. In the talk position, the light glows
The'remote stations can call the master station
through ‘a call-in circuit comprising conductors
with its greatest brilliancy as the plate current
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S8 and 10 connected to corresponding contacts 65 is greater.
associated with switches 56 and 58 of the selector
The operation of the system as a wholewill
switch 25. To condition the master station for
now be reviewed, it being assumed that the con
call in by remote stations, the switch blades 56
ductors 16 and ‘l8'are connected to a suitable
and'58 would normally be operated to complete
source of power, which may be eitheralternating
the circuit to conductors 681 and 18, but even 70 or'direct current; When thus connected, the
though this not be done, the circuit is completed
cathode heaters are all energized, they being
at all times by jumper conductors 1'2 and 14 con
connected in series across the power line. The
necting the switch blades 56 and 58 directly to
pilot light 82 glows with a brilliancy dependent
conductors 28 and 28.
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upon the position of the communication'direc
When the remote station desires to call the 75 tion and power controlling switch 24." Assuming
2,606,976
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, ?rst that the latter is .in
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secondary-of the output transformer. being. so
phased in relation to’ the primary ofj'the' jinput
idle position. the pilot
lightlglows with its lowest .brilliaiicyg'i
transformer that they are iniphasefiopposition at
the higher .frequencies, 1 passed I by; the ‘ ampli
fier, electroacouslticall[translating means, ‘a, sec
Assuming now that. the» masterstation desires
to communicate with station 3, the? station se
lector switch ~25 .is operated to its indicated posi
tion. The switch 24 is operated to, its talk'posi
ond .station having electroacoustical translating
means, and means comprisingmircuits. vincluding
an ungrounded two Jwirein‘tersltation.circuit, of
which one wire is common to both said translat
tion ‘and- the master station can then call the
remote station, the loud-speaker .2] being con
nected to the input and the loud-speaker 23 be
ing‘ connected to the output of the ampli?er. 10 ing means and tothe ampli?erii'nput and‘ ‘out,
put circuits, and is, permanen'tlyv Leo nected to
The pilot light glows'with its greatest brilliancy
said "?rst mentioned translating l'm'eans, and‘ ‘to
because resistor 88 is eliminatedfrom the recti?er
said transformers in saidv i?pllt; and output cir
circuit. To receive from .station 3, the-talk-listen
switch is returned to its listen position, which is
cuits and commuriicationlcontrot ‘su'rit'ch, means
at said ?rst station for, selec'trelygconnecting
ordinarily done simply upon releaseof the. switch
by a spring biasing it from its talk to its listen
said translating mean'sjlto the input and output
position.
circuits .of said amplifying means...
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.3. A communicationa‘system
v,Aft'er completion of the call, the selector switch
25 is returned to interconnect conductors .26 and
.‘ II
. Li f '
ehi'ding a ?rst
station having amplifying m I,
thjinputan'd
28 with the call-in circuit conductors 68=and 10. 20 output circuits, said input .fcircui liincluding a
transformer .and .a resistor l‘eonnectea across ‘the
However, even though this not be done, a remote
primary of said transformer, electroacoustical
station can .call the master station,.assumi-ng that
translating means, a .second'station having elec
the latter. leaves the switch 24 in itslisten'posi
troacoustical translating means, and means com
tion. All that is necessary fora remote station
ungrounded'twowire
,to call the master station is theclosure of switch 25 prising circuits including
interstation circuit, oiwhichgonejwireis. common
25C, whereby the loud-speaker at the remote sta
to both said translatingemeansf'a'nd to theiampli
tion is connected to the input of the ampli?er,
?er input and outputcircuits andfis permanent—
the loud-speaker 2| at the master station being
ly connected to said .?rstmentioiimd translating
connected to the output of the ampli?er.
means and to said transformers in‘_.‘saidfinpu-tland
The apparatus of the present invention has a
output circuits, and communication - control
number of advantages. The use of an un
switch means at said ?rst station for selectively
vgrounded common conductor reduces the number
connecting said translatingmeans to the'input
of switches and yet provides a substantially bal
and output circuits of ‘saidgamlplifyingmeansif
anced line. - Feedback and the pick-up of noise
4. A communication systemlir'icludingl. a ?rst
is minimized by the shield 50, the resistor 48, and
the phasing of the primary and secondary wind
ings of the input and output transformers, re
spectively. Another advantage is that the posi
tion of the switch24 is indicated by the pilot light.
This-is of particular vadvantage to a serviceman
who might be checking the operation of the ap
paratus. Also, the remote station can call in the
.master station even though theselector switch
25 not be returned to a particular position. Fur
thermore, the plate voltage supply is. controlled in
a, novel manner and includes the resistor ‘84 per
forming a number of functions as heretofore in
dicated.v
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station having audio frequent; amplifying means
with input and outputcirchi ,saidinput and
output circuits including,‘ transformers. and‘ ‘the
secondary of
output r'rsusfrsrmeepemg.so
phased in relationto 'theipri'mary .otthe' input
transformer that they are, in’. \phase._.opposition
at the higher frequenciespass'e ,ay theampli?er,
a resistor connected across the trimmer: said
input transformer, electroacoust'ical. translating ,
means, a second station h
electroacoustical
translating means, and means comprising ,circuits
including an. ungrounded two .iwire “interstation
circuit, ; of - which one; wires}. common to both
.
While the present invention- has been de
said translating means audio-the» ampli?er in
scribed in connection with the details of an illus
50 put and output circuits, an‘ ' communication con
trative embodiment thereof, it should .be under
trol switch means at said
stood that these details are not intended to be
limitative of the invention, except in so far as set
tively ‘connecting-said-transla ng
input and output
forth in the accompanying claims.
Having thus described my invention, what I 55
means.
claim as new and desire to secure .by Letters Pat
ent of the United States is:
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1. A communication system including a first
station having amplifying means with input and
output circuits, electroacoustical translating
60
V_
M station. for .selec
To
15;»:
to the
aidampiifying
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5. ‘A communication system including .a ?rst
station having amplifying-meanswith- input and
output circuits, , electroacousticalii translating
means, a plurality of .otherv'istations- each having
.electroacoustical translating means, means ,com
prising circuits includmgaftwowire interstation
means, a second station having electroacoustical
circuit for each of said-otherstations and a two
translating-means, and means comprising circuits
wire circuit .at the?rst station, of ‘which, circuits
‘including an ungrounded twowire interstation
one wire is common ‘to; both- aid translating
means and to the ampli?er inp ‘ nd~output cir
circuit, of which one wire is common to both said
means and to the ampli?er-input and- output
circuits and is permanently connected to said
?rst mentioned translating means and said input
and output circuits, and communication control
switch means at said ?rst station for selectively
connecting said translating means to the input
and output circuits of said ampli?er means.
2. A communication system including a ?rst
station having audio frequency amplifying means
with input and output circuits, said input and
cuits, and communication ontro witch?rneans
at Said. ?rst station tori-s, _ ec- vely connecting-"said,
translating means to the input and output. cir
cuits of said amplifying means, station selector
switch means at said ?rst station for selectively
connecting the two wire circuit thereat to those
of said other stations, and call-in circuits perma
nently connected to and extending from the two '
wire circuit at said one station to said other sta
tions, and switch means at each, of said other
output circuits including transformers and the 75 stations for connecting the electroacoustical
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2,606,976
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translating means at said ‘other stations to its
means, and additional resistance means insert
able in series with said resistor in one position of
,calle‘in circuit.
6. Intercommunicating apparatus including
said switch for controlling the input connections
amplifying means, a source ofpower for said am
of saidrecti?er.
plifying means, electroacoustical translating
means, a plural position communication control
switch means and control circuits associated with
said amplifying and translating means controlled
by said switch means for controlling the connec
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11. An intercommunicating system including
a ?rst station having amplifying means including
input and output circuits, electroacoustical trans
lating means, a communication circuit, and
switch means associated with said amplifying
means and translating means for connecting said
communication circuit and translating means to
tion of said translating means to said amplifying
means, a pilot light, and means includingplural
position switch means operable with said com
the input and output circuits, respectively, of
munication control switch means and associated
said amplifying means, a second station including
with said power source and pilot light controlling
electroacoustical translating means, interstation
circuits controlledby said last mentioned switch 15 communication and call-in circuits connecting
means for supplying said light with different
said last mentioned translating means to said first
amounts of power to cause it to glow with dif
station, station selector switch means at said ?rst
ferent brilliancies in di?erent positions of said
station associated with both said communication
communication control switch.
circuits for connecting them, and a circuit per
7. Intercommunicating. apparatus including 20 manently connecting said call-in circuit to the
amplifying means, a source of power for said am
communication circuit at said ?rst station.
plifying means, electroacoustical translating
' 12. An intercommunicating system including a
means, a three position communication control
?rst station having amplifying means including
switch means and control circuits associated with
input and output circuits, electroacoustical trans
said amplifying and translating means controlled 25 lating means, a communication circuit, and switch
by said switch means for controlling the connec
means associated with said ampifying means and
tion of said translating means to said amplifying
means, a pilot light, and means including three
translating means for connecting said communi
with said power source andpilot light controlling
electroacoustical translating means, interstation
communication and call-in circuits connecting
cation circuit and translating means to the input
position switch means operable with said com
and output circuits, respectively, of said ampilfy
munication control switch means and associated 30 ing means, a plurality of other stations including
circuits controlled by said last mentioned switch
means for supplying said light with three dif
ferent amounts of power to cause it to glow with
said last mentioned translating means to said ?rst
station, a plural position station selector switch
three di?’erentybrilliancies in different positions 35 at said ?rst station associated with said com
of said communication control switch.
munication circuit and said interstation circuits
8. Intercommunicating apparatus including
for selectively connecting them, said call-in cir
amplifying means, a source of power including
cuits all extending to one position of said selector
rectifying means for said amplifying means, elec
switch, and a jumper circuit permanently con
troacoustical translating means, a three position 40 necting said call-in circuits to the communication
communication control switch means and control
circuit at said ?rst station.
circuits associated with said amplifying and
13. Intercommunicating apparatus including
translating ‘means controlled by said switch
means for connecting said translating means to
the input or output of or disconnecting it from
said amplifying means, a pilot light, and means
including a three position switch means'con
nected to said communication control switch
‘plural position communication control switch
means, a light, and means including a power
415
source, light intensity controlling means in cir
cuit with said light and power source, and means
operatively connecting said controlling means to
said communication control‘ switch means for
means and associated'with said rectifying means
supplying power to and causing said light to glow
and pilot light controlling circuits including re 50 at different brilliancies in different positions of
sistance means controlled by said last mentioned
said switch means.
switch means for supplying said light with three
RICHARD H, CAMPBELL.
different amounts of power to cause it to glow
with three different brilliancies in different posi
REFERENCES CITED
tions of said communication control switch.
9. Intercommunicating apparatus of the type
including amplifying means,‘ comprising a recti
The following references are of record in the
?le of this patent:
UNITED STATES vPATENTS
?er connected to said amplifying means, and
means including switch means and a series re
sistor at the input side of said recti?er control
ling the power input connections of said recti?er.
10. Intercommunicating apparatus including
amplifying means, a recti?er connected to said
amplifying means, and means including a series
resistor, a multiple position communication con 65
trolling switch associated with said amplifying
Number
Name
Date
2,107,817
2,162,369
Davis _____________ __ Feb. 8, 1938
Campbell ________ __ June 13, 1939
2,162,370
2,269,144
Campbell ______ __'__ June 13, 1939
Campbell ____________ Jan. 6, 1942
2,275,406
Berkley __________ __ Mar. 10, 1942
2,326,616
Campbell _________ __ Aug; 10, 1943