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Патент USA US2378388

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June 19, 1945.
_
5. J. BEGUN
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2,378,388
‘RECORDING AND REPRQDUCING DEVICE
Filed Jan. 1, 1942
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June 19, 1945.
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RECORDING AND REPRODUCING- DEVICE
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I ZTTORNEY
June 19, 1945.
5. J. BEGUN
2,378,388 I
RECORDING AND REPRODUCINGI DEVICE
Filed Jan. 1, 1942
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2,378,388
Patented June 19, 1945
UNITED STATES PATENT OFFICE
2,378,388
RECORDING AND REPRODUCING DEVICE
Semi Joseph Begun, Cleveland Heights, Ohio, as
slgnor to The Brush Development Company,
Cleveland, Ohio, a corporation 01' Ohio
Application January 1, 1942, Serial No. 425,304
31 Claims. (Cl. 171-95)
Figure 2, showing the transient recording cir
This invention relates to systems and methods
cuit in detail and the trigger circuit and the
for studying transient phenomena and more
transient reproduction circuits in block diagra
particularly to such systems and methods for re
cording on a recording medium a transient cir
form and connected to the transient recording‘
cuit condition and utilizing the record of the
transient for studying the characteristics of the
circuit.
Figure 5 is an illustration of the trigger circuit
and showing the recording and reproducing cir
transient.
,
v
Among the objects of the invention are novel , cuits in block diagram form.
Figure 6 is an illustration of the circuit used
systems and methods of the foregoing type which
operate to make a continuous obliterable record 10 ‘for reproducing the transient, and showing the
recording and trigger circuits in block diagram
of the circuit conditions under study on an end
form and connected to the reproducing circuit.
lessly-operating cyclically-effective recording me
Figure '7 is a plan view of a magnetic head in
dium, such as a magnetic recording medium, so
its open position.
that the circuit conditions are continuously re
corded; the continuous recording operation be 15 Figure 8 is a plan view of the magnetic head
in its closed position.
.
ing accompanied by a continuous obliteration
Figure 9 is a diagrammatic illustration of a
of the recordings and the obliterating action be
timing device utilizing my transient recording
ing stopped upon the occurrence of a transient
device.
condition so as to retain on the recording medium
a record of a signal corresponding to the tran 20 My invention comprises means and a method
for recording a transient signal'on a storage me
sient occurrence and the recording operation be
ing discontinued after the transient occurrence
dium and repeatedly reproducing it therefrom
has been recorded on the medium in such man
ner as to enable the study of the transient oc
atv regular intervals to establish a wave, each
cycle of which is substantially a facsimile of the
currence by cyclically reproducing the record
and utilizing the reproduced record for operating
. original transient.
The device may use any re
cording medium, and suitable means for record
ing the transient thereon and reproducing the
a cyclically-operative indicating device, such as
transient therefrom. I prefer to use a medium
an oscilloscope, which presents an image corre
which can be used over and over again such, for
sponding to the reproduced signal upon each
cycle of the recording medium; such systems 30 example, as a magnetic tape or disc, etc.
Such preferred embodiment is illustrated in
and methods which are effective for studying low
Figure 1, in which is shown means for a method
frequency and direct current transients by modu
of storing a transient by electrically recording it
lating with the signal which is to be recorded a
on an endless magnetic tape l0, means for and
source of carrier oscillations of a frequency
which is reproducibly recordable on the endless 35 a method of reproducing the recorded transient
from the recording medium and presenting it
magnetic recording medium, so as to provide a
visually by repeatedly reproducing it on an oscil
modulated carrier signal which is continuously
lograph I I or other indicating device; and associ
recorded on the endless recording medium and
ated circuits for controlling the operations of the
obliterated immediately thereafter, the obliterat
ing action being stopped upon the occurrence of a 40 means and method. Electrical recording may in
elude electromagnetic, photoelectric, or any
transient—the reproduced recorded modulated
other process or device utilizing electricity in the
signal being modulated so as to cyclically provide
recording and/or reproducing process.
.
a demodulated reproduced signal corresponding
The'endless tape I0 is driven about rollers 12
to the transient signal which is utilized for oper
ating the cyclically operative indicating device; 45 and 13 by a motor l4. A magnetic obliterating
head I5 and a magnetic recording head l6 are
and various other novel and desirable features
associated with the tape Ill. The obliterating
forming part of such systems.
head I5 is adapted to apply a steady saturating
The foregoing and other objects of the inven
?ux (such as the ?ux derived from battery H)
tion will be best understood from the following
to the tape ID as the tape passes, and to bring
description of exempli?cations thereof, reference
each incremental portion of the tape to a state
being had to the accompanying drawings where
of substantially uniform saturation. With the
switch 23 closed in its downward position the re
Figure 1 is an illustration of my invention in
cording head It is connected to a signal record
block diagram form.
Figure 2 is an illustration of another form of 55 ing circuit which may include a source I 8 of
polarizing current. The transient signal to be
my invention, also in block diagram form.
recorded on the tape I0 is applied at the input
Figure 3 is a diagrammatic illustration of a
terminals I9, 20, of the recording circuit. In
modulated carrier current and a magnetization
cluded in the recording circuit is an ampli?er
curve.
Figure 4 is an illustration of the circuit of 60 2| and an equalizer 22. The equalizer 22 is to
in
.
'
2
2,878,388
provide substantially constant current to the re
cording head IS. The instantaneous current
which is in the recording head I6 is given by the
superposition of the instantaneous values of the
transient signal current and the polarizing cur
rent. As the saturated tape passes the record
ing head a magnetic pattern corresponding to
the current in the recording head is recorded
on the tape in the well-known manner, and as
quency modulation and phase modulation. A de
tailed description of one carrier method of re
cording may be found in my application entitled
Apparatus and method for magnetic recording,
Serial No. 399,909, ?led June 26, 1941.
‘
Figure 2 illustrates a form of my invention
adapted to record transients in direct current
circuits or circuits normally carrying no current,
and using the method detailed in the above-cle
soon as‘the transient has been recorded the ob 10 scribed patent application. ;Examples of tran
literatin‘g and recording process are stopped by
sients which this particular form of the apparatus
automatically or manually opening'switches 23
is adapted to record are the current in spot weld
and 28 so that the recorded transient will not be
ers and the charge or discharge of condensers,
erased or have further transients superimposed
etc.
upon it. A playback‘ head separate from the re
The input terminals I9, 20 are connected to
cording head l6 may be used in association with
the circuit in which a transient is expected, such
the endless tape III by connecting it to an equal
for example, as across a low resistance in the
izer 24, an ampli?er 25, and the oscilloscope Ii
circuit of an impact welder. The motor il drives
the roller l2 to cause the endless magnetic tape
or"_other indicating device, but I prefer to use
the'recording head IS in a dual capacity; that is, 20 III to continuously rotate about rollers l2 and I!
as both a recording and playback head, and pro
at a uniform velocity in the direction shown by
- vide the switch 23 for switching the head I6 from
the arrow. The time of one cycle of the tape loop
the recording circuit to the playback circuit.
preferably is slightly longer than the transient
After the transient, which may occur only once,
which may, for example, be of about one-tenth
-isl»recorded on the endless tape ill, the tape can be 25 of a second duration, thereby establishing on the
tape loop a record of the normal circuit condi
driven around the rollers l2, l3 and, with switch
23 thrown to cause the head IE to act as a play
back head, each complete transit of the tape will
tions and a record of the transient condition. An
oscillator 26 is tuned to a frequency somewhat
higher than the highest frequency component to
cause the signal recorded on the tape to produce
a trace of the transient on the oscillograph I I. In 30 be recorded. When the highest frequency com
ponent of the signal is in the neighborhood of
this manner repeated reproduction of the tran
sient signal on an oscilloscope II, in which the
500 cycles per second a carrier frequency on the
horizontal sweep of the oscilloscope is synchro
order of 2000 cycles per second is satisfactory.
nized with a point on the tape ill, will produce
The oscillator is connected to and caused to ex
a su?iciently bright and sustained trace to enable 35 cite an obliterating ampli?er 21, which in turn
supplies 2000 cycle current to the obliterating
a person to study the transient, and no time need
head l5. As the tape l0 passes the obliterating
head l5 each incremental portion of the tape is
subjected to a 2000 cycle alternating magnetic
a switch.
If the transient is of an acoustical nature it 40 force which is suf?ciently strong to saturate the
part of the tape closest to the coils. As each in
' may be converted by means of an electromechan
cremental portion of the tape leaves the coils the
ical transducer vinto an electrical transient and
applied at the input i9, 20 of the recording'cir
magnetic ?eld active on it is gradually reduced
be lost between the recording and playback oper
ations other than the time necessary to throw
and thus the successive increments of the tape are
cuit. In this manner an acoustical transient may
be studied the same as an electrical transient, 45 brought to an unmagnetized state. In this con
dition the tape is ready to have a new record
also, transients of a physical nature such as pres
sure, etc, may be changed to electrical tran
sients and recorded for study.
iliéipressed on it at the magnetic recording head
The oscillator 26 also supples 2000 cycle car
With the above described method it is di?icult »
to reproduce the recorded signal from the mag 50 rier current to the magnetic head IE, but before
reachingthe magnetic head I6 the carrier cur
netic medium if the signal has low frequency
rent passes through a modulator 29 to which
components as the rate of change of flux in the
is also connected the transient signal input ter
magnetic head is low for the low frequency com
ponents. For the above described means and
minals I9. 20. In the modulator 29 the transient
method of recording this makes necessary‘ the 65 signal modulates the 2000 cycle carrier current
use of considerable equalization for low frequen
from the oscillator, and the signal modulated
carrier then passes to an ampli?er 30. The mod
cies with consequent introduction of phase shift
ulator 29 is of the balanced type arranged to bal
and background noise. With this method the
ance out the signal and pass the modulated car
quick interruption of the recording and obliterat
ing current by throwing switches 23 and 28 after 60 rier. A high pass ?lter 3I- may be connected in
the recording circuit between the ampli?er 30
the signal transient is on the tape causes an un
and the magnetic head iii. For recording tran
desired transient to be recorded on the tape which
sients whose highest frequency components are
is apt to interfere with the desired signal tran
in the neighborhood of 500 cycles per second the
sient.
In order to obviate these undesirable con 65 high pass ?lter may be designed to cut off some
what below 1500 cycles. The exact point at which
ditions I use a signal modulated carrier cur
the high pass ?lter cuts on‘. depends upon the fre
rent to record on the tape. i‘his method per
quency range of the transient to be recorded and
mits the recording without phase distortion
upon the chosen carrier current frequency. The
of frequencies substantially down to zero fre
quency corresponding to direct current, and can 70 ?lter 3i is not essential but is useful in taking
out hum and the residual transient signal which
be arranged to avoid introduction of undesirable
may have gotten through the modulator 29. If
transients caused by switching operations. Sev
no transient is being recorded the 2000 cycle al
eral methods of modulating a carrier current to
ternating ?ux set up in the magnetic head I6 by
record on the magnetic medium may be used;
among them being amplitude modulation, fre 75 the carrier current causes a 2000 cycle magnetic
2,378,888
wave to be recorded on the moving tape Ill. Upon
nearly completing a. circuit of rollers I2, I 3, the
recorded wave is removed by the obliterating
3
time intervals such that it can be viewed on a
cathode ray oscillograph.
The oscillograph H shown may be a standard
commercial cathode-ray oscillograph, such as
head l5.
When a transient signal is applied to the signal Cl type TMV—122—-B sold by the Radio Corporation
of America, as described in its instruction book
input terminals I9, 20, the carrier current is mod
IB-23,339, published in 1937. As is well known,
ulated by the transient and a corresponding mod
such standard cathode-ray oscillographs are
ulated magnetic carrier wave is recorded on the
equipped with a synchronizing switch which is
tape. To prevent obliteration of the transient
modulated magnetic carrier wave, and to avoid 10 used to control the synchronization of the hori
zontal time-axis sweep with the investigated sig
nal. The synchronizing switch usually has at
after the tape H] has completed a cycle around the
least two positions, namely, an internal syn
rollers l2, l3, a transientpperated control circuit
chronizing position, in which the time-axis sweep
is energized to block the obliterating ampli?er 21
and to open the recording circuit after suitable 15 is automatically synchronized with the investi
gated input signal, and an external synchroniz
time intervals.
ing position, in which the time-axis sweep is syn
The gain of the ampli?er 30 which feeds the
chronized with an external synchronizing signal.
magnetic head I6 is preset to swing the record
The number of repetitions per second at which
ing ?ux set up in recording head l6 by the carrier
current, over the proper part of the magnetic 20 the recorded transient is repeated on the oscillo
graph II depends on the number of tape cycles
curve of the tape. (This is explained in detail in
per second. For example, this frequency of repe
connection with Figure 3.) The strength of the
tition may be ten transient facsimiles per sec
transient signal input may be adjusted by a po
ond on the oscillograph. The time-axis sweep
tentiometer 32 connected across the signal input
of the cathode-ray may be internally synchro
terminals 19, 20.
nized with the reproduced, demodulated and ill
The transient operated control circuit consists
tered signal, which is impressed upon the oscillo
of a trigger device 33 connected to the transient
graph II, or the tape joint 49 or a nick in the
signal input terminals I9, 20, the obliterating am
tape maybe used as a trigger for synchronizing
pli?er 21, switching means 34, and sometimes, if
desired, to a switch 41 connected to the tape 30 the time-axis sweep of the cathode-ray.
In order to record on the steel tape l0 an elec-'
drive motor I4. The trigger means is actuated by
tric current is used to set up a proportional mag
the incoming transient to cause the obliterating
netizing force which is applied to the tape l0.
ampli?er 21 to be blocked thereby preventing the
Therefore, as the electric current varies in ac
obliterating head I5 from “erasing” the record of
the transient which is made on the moving tape 35 cordance with the instantaneous value of the sig
nal to be recorded, the magnetizing force im
I 0, and the actuation of the trigger means 33 also
pressed on the tape varies in proportion to the
causes the switch means 34 to be thrown to break
original signal.
the recording circuit to the magnetic head I6 and
The relationship between the magnetizing force
to make ‘a playback circuit from the magnetic
head Hi to the indicating instrument II. If 40 H and the resultant magnetic induction B for in
desired the trigger circuit may iloe used to break ' creasing and decreasing values of H is expressed
graphically by a hysteresis loop, and for increas
the circuit to the motor l4 and stop the tape l0
ing values of H starting with a demagnetized tape
immediately after a transient has occurred.
it is expressed by a virgin magnetization curve.
Thus, shortly after a transient has been recorded
on the tape I0, the entire device automatically 4.5 Every magnetic material has a particular virgin
magnetization curve and hysteresis loop which
becomes inoperative due to the action of the trig
identi?es the magnetic characteristic of the ma
ger means.
terial.
~
.
For applications in which it is not desired to
From hysteresis loops it is obvious that mag
have an automatic control of the trigger circuit,
an external control 4| is provided. The external 50 netic effects are not reversible, and that the mag
netic induction obtained from a given magnetiz
control may be a push button or other similar de
ing force depends upon the previous magnetic his
vice for initiating the action of the trigger device
superimposing the carrier on the recorded wave
33 to effect the same results as the actuation of
the trigger device 33 by the incoming transient
signal.
After the transient is recorded on the tape II]
in the form of a modulated carrier magnetic re
cording, it is ready to be observed by repeatedly
tory of the material on which the magnetizing
force is impressed. Accordingly, with a tape upon
55 which previous magnetic records have been made
it is necessary to produce a substantially uniform
condition either of saturation or demagnetiza
tion in order to "erase” the magnetic record.
In a. magnetic tape it is necessary to obliterate
reproducing the tape record on an oscillograph
II or other indicating instrument. From the 60 the previous record before a new record is put
on the tape or mixed records are apt to result.
magnetic pickup head I B the reproduced signal
This obliteration may be obtained by applying a
goes through an ampli?er I30 then through a
magnetizing force to the tape which is sui?ciently
band pass ?lter 36 which is designed to pass,
high in value to cause an induction which is in
in addition to the carrier, the side bands corre
sponding to modulation frequencies up to about 65 the saturation range on the magnetization loop
of the material. That is, in the neighborhood of
500 cycles. The signal then passes to the de
point S1 or S2 in Figure 3, in which the heavy line
modulator 31 where a recti?er “detects” the out
38 represents a typical virgin magnetization curve
put of the band pass filter and the carrier and
for a material which has been demagnetized.
its harmonics are ?ltered out, and then to an in
> dicating instrument such as an oscillograph I I. 70 The obliteration may also be obtained by apply
ing over a relatively large area" of the moving
The output from the demodulator consists of a
tape an alternating magnetizing force derived
direct current component upon which is super
imposed a wave composed of a series of tran
from an alternating current, and gradually re
ducing the magnetizing force to zero to reduce
sients each one being substantially a facsimile of
the original transient, and following at regular 75 the residual magnetism to substantially zero.
4
2,878,388
signal will have a 3-H relationship in accordance
with the virgin magnetization curve 33 of the
inates the need for an extra oscillator and makes
a more simple device. However, if the need
arises it is to be understood that the obliterating
material. The decrease in strength of the mag
netizing force is obtained for each portion of the
current and the carrier current may be produced
by separate sources (such as oscillators) and
tape by removing that portion of the tape farther
and farther from the center of the magnetizing
that the obliterating current frequency may be
of any value which will give a su?icient number
force.
of reversals of polarity to reduce the residual
Subsequent magnetization in accordance with a
This is the method of obliteration em
magnetism in' the tape to substantially zero.
In Figure 3 the line 38 represents a magnetiza
‘ Continuous alternating current is applied to In
tion curve for a material which may be used as
the coils‘ of obliterating pole pieces which are
a magnetic tape. The curve comprises two sub
positioned near the moving tape. This causes
stantially straight portions 232 and 233 and three
a rapidly reversing diffuse magnetic ?ux to be
curved portions 234, 235, and 238. The curved '
impressed- through an area of the tape which is
portion 236 lies between the two substantially
large in comparison to the area through which
straight portions 232 and 233 and represents non
the recording flux is impressed, and as each por4
linearity between the magnetizing force and the
tion of the tape ‘moves away from the pole pieces
induced ?ux density for small values of the mag
which are the center of the flux distribution, the
netizing force. From zone 231, which is sub
strength of the ?eld on each such portion of the
stantially the junction of curved line 236 with
tape decreases gradually to zero. The pole pieces
line 232, to zone 238, which is substantially the
of the obliterating head have their like magnetic
junction of line 232 with curved line 234, the line
poles toward each other. However, the use of
ployed in the preferred form of my apparatus.
alternating current in the coils causes the mag
netic polarity of each pole to alternate; at one
instant the north poles are toward each other,
the next instant the south poles are- toward each
other. This establishes a magnetic ?eld about
each pole piece which bucks the other magnetic
232 is substantially straight. This means that for
each unit increase in magnetizing force H be
tween zones 231’ and 238' there is substantially a
proportional increase in the flux density B in
the tape I0 from 231" to 238". Above zone 238
partial saturation takes place and B does not
?eld and results in a relatively large leakage or
diffuse magnetic ?eld through which the tape .
moves during the obliterating process
Each portion of the tape which has been re
increase on a substantially constant ratio with H.
Below the H axis the same effects take Place for
magnetizing forces created by currents of the
moved suf?ciently far from the obliterating poles
tion of lines 236 and 233; and zone 240 repre
sents the junction between lines 233 and 235.
Zones 231, 238, and 239, 240 may be referred to
is now reduced to substantially zero residual mag
netism and is ready to have a magnetizing force ;
corresponding to a signal impressed on it. This
is done by the recording head indicated generally
by the reference character It and comprising
opposite polarity. Zone 239 represents the junc
as critical zones or points as they de?ne substan
tially the extremities of the substantially straight
portions of the magnetization curve.
In order that a signal recorded on the tape Hi
two pole pieces, one of which is surrounded ‘by a
coil. In the coil there is a current correspond 40 can be reproduced without considerable distortion
it is necessary that the maximum magnetic ?ux
ing to the signal to be recorded on the tape. The
induced in the tape during each cycle of the mod
current establishes a varying magnetizing force
ulated carrier current correspond to a point
in the pole piece which in turn establishes vary
which lies on the substantially straight portion
ing magnetic flux density in successive portions
45 232 or 233 of the magnetization curve of the ma
of the tape.
terial.
Figure 3 diagrammatically illustrates my pre
Figure 3 further illustrates how the magnetiz
ferred method of recording a low frequency tran
ing forces H corresponding to a modulated car
sient on a magnetic materlalwhich has pre
rier current induce maximum magnetic ?ux den
viously been demagnetized to substantially its
virgin state, and comprises modulating a carrier 50 sities in the tape l0 which correspond to points
on the straight portions 232 and 233 of the mag
frequency current 39 by the transient signal to
establish two envelopes 40, and applying to the
netization curve of the tape material, and how
tape l0 magnetizing forces having successive
distortion in the reproduced signal may be re
peak values corresponding to both of the en
duced by preventing the maximum flux densities
velopes 40, and by adjusting the modulation of 55 for each cycle in the tape from corresponding to
the carrier current by the signal to cause it to
points on the curved portions 234, 235, and 233
be at all times below 100 per cent.
of the magnetization curve of the material. This
Recording a signal on a tape introduces con
may be referred to as recording on the substan
siderable distortion due to non-linearity of por
tially straight portions of the curve. In record
tions of the magnetization curve of the tape ma 60 ing a substantially symmetrical transient on a
terial unless steps are taken to cause the re
substantially demagnetized tape by my modulated
cording to be only on the substantially linear
carrier current system, the greatest dynamic
portions of the magnetization curve. I effect re
range can be obtained by adjusting the normal
cording on the substantially linear portions of
peak amplitude of the unmodulated carrier cur
rent to have a value which corresponds to a mag
the magnetization curve of the tape material by
netizing force H having a value which lies sub
applying to the coils a current comprised of a
stantially midway between the value of the forces
carrier current modulated by a signal to be re
corresponding to zones or points 231' and 238'.
corded, the highest value of the modulated car
The value of this force is represented by the point
rier current being insufficient to cause magnetic
saturation in the tape l0, and the percentage of 70 having the reference character 245. Point 248
modulation of the carrier by the signal being at
represents the value of this force for the opposite
all times substantially less than 100 per cent.
polarity of the carrier current. The minimum
I have found that for most carrier frequencies
amount of distortion‘ due to recording on the
the same oscillator can be used as a source of
curved portion of the magnetization curve is ob
both carrier and obliterating current. This elim 75 tained by adjusting the percentage of modulation
2,378,888
5
Fig. 4' is supplied by the power supply P1 which
may be of conventional design.
of the carrier current to a value which is at all
times su?lciently below 100%: that is, with the
The modulator 29 comprises a pair of pentode
tubes 15, 16 with plate and screen voltage stabi
lized by a glow tube voltage regulator 11. Car
rier signal supplied by oscillator 26 is applied in
opposite phase to the grids of the two modulator
tubes by center tapped transformer 64. The
produced by each cycle of the modulated carrier
transformer secondary 66 is tuned to the oscillator
current will not be greater than the value of
the magnetization force H represented by the 10 frequency by shunt condenser 18. The transient
signal derived from potentiometer 32 connected
points 238 and 240, nor less than the value of
the magnetization force H represented by the
across input terminals I9 and 20 is supplied in
the same phase to both modulator grids through
points 231 and 233. I have found that 50 to 60
per cent modulation is satisfactory for some mag
the connection 80 and the center tap of the trans
netic materials. By this process the maximum 15 former secondary 66. Bias for the modulator
tubes is produced by the‘ plate and screen current
values of the ?ux densities, in the tape for each
?owing through resistor 19. The plates of the
carrier cycle correspond to points which lie only
on the substantially straight portions of the mag
modulator are connected in push-pull fashion to
the center tapped primary I45 of transformer 85.
netization curve of the material, and therefore
distortion of the signal reproduced from the en 20 The secondary of this transformer supplies the
modulated carrier to ampli?er 30. Since the
velope of the carrier is reduced to a minimum.
The magnetizing force H corresponding to the
transient signal is applied to the two grids in the
same phase while the plates of the tubes are con
amplitude of the peak of each cycle of the mod
nected in push-pull fashion, the transient signal
ulated carrier current is always less than the
itself cannot appear at the secondary of the out- '
value of zones or points 236', 240’, to prevent
recording on the curved portions 234, 235 of the
put transformer, provided that the modulator cir
magnetization curve, and is always greater than
cult is properly balanced. Presence of the tran
sient signal itself in the recording circuit is un
the value of zones or points 231', 239' to prevent
recording on the curved portion 236 of the mag
desirable as it may interfere with proper record
netization curve. Depending upon the material 30 ing of the modulated carrier. Rather than pro
vide means for accurate balancing, a high pass ?l
used for the endless tape the size of the curved
ter 3| is employed at the output of. the ampli?er
portions 234, 235, and 236 varies and the degree
of curvature of the substantially straight por
to ?lter out any residual transient signal due to
modulator unbalance.
tions varies. For each kind of tape it is possible
The oscillator 26 employs a dual triode 55.
to adjust the amplitude of the unmodulated car
normal peak amplitude of the carrier current ad
justed substantially midway between zones or
points 231' and 238’ for one polarity and be
tween zones or points 239 and 240 for the other
polarity, the peak value of the magnetizing force
The oscillator circuit proper is of the resistance
rier current to cause the normal peak value of
stabilized Hartley type and employs one triode
section 56 of the tube 55. The frequency deter
points 231' and 238’ and between 238' and 240',
mining elements are tapped inductance 59 and
and to adjust the amount or percentage of modu
lation of the carrier current by the signal to be 40 condenser 60. Resistor BI is the stabilizing re
sistor and 63 is a blocking condenser. The plate
recorded to cause the peak value of each cycle
circuit is supplied through choke coil 42. The
of the modulated carrier current to lie between
tube is biased by means of the cathode resistor
points 231' and 238’ for one polarity of the car
5| which is bypassed by condenser 52. The sec
rier current, and between points 239' and 240' for
45 ond section 51 of the tube 55 is employed as a
the other polarity of the carrier current.
buffer ampli?er. Its grid is connected through
In certain applications, the transients to be re
blocking condenser 46 to the plate end of the
corded will all be of the same general nature and
oscillator coil 59 and has a bias path to ground
may consist of unidirectional pulses. A typical
through grid leak 48. In the plate cathode cir
example is the transient voltage developed across
each cycle to fall substantially half way between
cuit are connected three impedances, plate re
a resistor when a condenser is discharged there
through. In such cases, the amplitude of the
unmodulated carrier may be so adjusted that the
resulting magnetizing forces, corresponding to the
peak values of the wave, fall near points 237 and
233 and the transient circuit so connected that '
the carrier is modulated upwardly toward but not
exceeding points 238 and 240; or downward
modulation may be used with unmodulated car
rier peaks producing magnetizing forces falling
near points 238 and 240. For cases between sym
metrical transients and completely unsymmetri
cal transients, intermediate carrier amplitudes
may be used. By following this procedure thus
substantially straight portion of the virgin mag
netization curve is used to the maximum advan
tage.
Detailed description of recording circuit
Figure 4 is a detailed circuit of a transient sig
nal recording means somewhat similar to the re
cording means of Figure 2 but differing in that
a single ampli?er is shown, and relay 34 does not
sistance 44, bias resistor 45, and primary 65 of
the modulator input transformer 66. The plate
voltage for both sections of the tube is stabilized
by the same regulator tube 11 that functions
for the modulator. The ampli?ed carrier voltage
developed across resistance 44 is supplied to the
obliterating ampli?er 21. Carrier current flow
ing through primary 65 supplies carrier signal
to the modulator. Resistor 45 supplies bias for
60 the buffer tube and also introduces some degen
eration.
The ampli?er 30 is a two stage resistance
capacity coupled type of conventional design. A
?xed voltage divider comprising resistors 16 and
‘H is provided at the input to select a suitable
portion of the modulated carrier output of modu
lator 29. The output of the second stage ampli
?er tube 81 is coupled to high pass ?lter 3|
through a suitable matching transformer BI and
the output of the ?lter is supplied via switch or
relay 34 to recording head I6. The high pass
?lter 3| is of a simple con?guration, compris
ing two condensers 88 and inductance 89.
The carrier frequency supplied by the oscilla
make the playback circuit.
,Plate power for the various tubes detailed in 75 tor, and the frequency response characteristics
1
2378.838
6
I 05 which is not energized during the recording
of the associated circuits just described depend on
process.
the range of transient frequency components to
A trigger relay circuit (to be described later)
be recorded. For transient components up to 500
is provided to block the amplifier to cut off the
cycles per second, the carrier frequency may be
obliterating current a short time after the tran
2000 cycles. The modulator input transformer
sient occurs and just before the recording of
circuit would then be tuned to 2000 cycles and
the transient modulated carrier reaches the oblit
the low pass ?lter would have its cuto? frequency
erating head. This is done by causing the trigger
somewhat below 1500 cycles to allow for tran
circuit to energize relay I05 which breaks the
sient signal side bands. The ampli?er 30 will
be required to pass frequencies only in the range 10 ground connection for grid resistor I00 and con
I nects the resistor to a negative bias tap I09 of
of 1500 to 2500 cycles and may be designed ac
‘power Supply P1. This bias is sumcient to stop
cordingly.
the flow of plate current to tube 01 and thereby
The magnetic head l6 functions as a recording
head and is connected to the recording circuit - ‘stop the obliterating process. Condenser I08 is
only as long as the trigger relay switch 34 has 15 connected into this bias circuit to slow down the
blocking process to prevent the recording or an
not been actuated by trigger means 33 to cause
undesired transient which might result if the
it to become inoperative. Shortly after a tran
obliterating process were stopped suddenly.
sient signal is applied to the signal input ter
The“ obliterating head I5 has two pole pieces,
minals I9, 20 the trigger relay becomes opera
ll6‘and II6, surrounded, respectively, by coils
tive to cause the magnetic head to be discon
II‘! and H8. The two coils are connected in
nected from the recording circuit to prevent
' series opposing relationship so that at any instant
superimposing extra signals in the desired re
corded transient. The actuation of the trigger ' the adjacent ends of the pole pieces have the
same polarity, thus causing a di?use magnetic
circuit also blocks the obliterating ampli?er
?eld in the neighborhood of the tape.
which prior to the coming of the transient has
been continuously “erasing” the record of the
Details of trigger circuit
carrier on the tape I0. Blocking the obliterat
Simultaneously
with the recording of the
ing ampli?er prevents the ampli?er from erasing
transient signal on the moving tape I0, the tran
the transient signal which has just been recorded
sient actuates a trigger circuit shown in detail
on the tape.
80 in
Figure 5 to cause (after a certain time delay)
The use of an obliterating current which grad
the obliterating head to stop “erasing" the signal
ually reduces the magnetism in the tape III to
which is on the tape, and to cause the magnetic
zero prevents a transient from being recorded
head I6 to stop recording on the tape. The in
on the tape due to the sudden blocking of the
obliterating current, and the use of the modu 35 terval between the time when the ?rst part of
the transient signal is put on the tape I0 and the
lated carrier current recording process prevents
time when the obliterating and magnetic heads
a transient from being recorded on the tape due
I5 and I6 cease to be operative should be slight
to the sudden disconnection of the recording head
ly less than the time interval for one cycle of the
from the recording circuit.
40 tape.l0 around the rollers I2 and I3. This as
Obliterating ampli?er
sures that there will be no superposition of an
other signal on top of the already recorded tran
sient signal, and if the tape is long enough the
entire transient will be recorded. In other words,
the trigger circuit synchronizes the recording
cycle with the time period in which the transient
occurs; and in addition governs the length of
which the unmodulated carrier is recorded on
time of the recording cycle, this time being a
the tape I 0, that is, during the time that the
function of the speed and the length of the end
apparatus is in operation in anticipation of the
occurrence of a transient, the coils of the oblit 50 less tape. It is essential that overlapping in the
recording process be avoided, meaning that the
erating head I5 are energized by an alternating
recording period should be stopped before the
current of su?icient strength to saturate mag
tape I0 has completed a cycle around the rollers
netically the portions of the tape immediately
I2 and I3.
Y
adjacent the head. For convenience, this oblit
erating current is obtained from the oscillator 55 A gas tetrode tube I 33 has in its plate circuit
the coils of relay I05 which when energized
26, a single stage ampli?er 21 being interposed
blocks the obliterating ampli?er and relay I62
to obtain su?lcient current and to isolate the
which interrupts the recording process. Normal
head from the oscillator. The obliterating am
1y, this tube is non-conducting and the relays
pli?er 21 comprises a power pentode tube 91
whose plate is coupled to the obliterating head 60 I 05 and I62 are not energized. Its control grid
I58 is connected through variable resistance I6I
by means of transformer I02. Condenser I04
to the cathode of another gas tetrode I32 which
tunes the obliterating head circuit to the fre
also normally is non-conducting. Grid I58 is by
quency of the oscillator so that maximum cur
passed to ground by condenser I60. When the
rent may be obtained. Plate current for the tube
91 is supplied by power supply P1 which may 65 gas tetrode I32 becomes conducting the voltage
drop across cathode resistor I 51 applies a posi
be of conventional design. Normal operating bias
tive bias to grid I58 thus "?ring” gas tetrode I33
is provided by cathode resistor IOI which is by
and thereby energizing relays I05 and I62. Re
passed by condenser III. Oscillator 26 ener
sistor I 6| and condenser I60 introduce a time
gizes control grid 98 through the connection 95
and blocking condenser 96. Grid 98 is main 70 delay, depending on the values of these two com
ponents so that the relays are energized at a pre- ’
tained at the proper negative bias potential by
determined interval of time after the “?ring” of
the direct current path to ground comprising
tetrode I32. This tube is "?red” by the transient
resistor 99 in series with the parallel combina
signal and the time delay provided by resistor
tion of resistor I01 and resistor I00. Resistor
I00 is grounded through the contacts of relay 75 IN and condenser I60 is so adjusted that the
Figure 5 illustrates the details of the obliterat
ing and trigger circuits in connection with the
recording and playback circuits which are shown
in block form.
During the part of the recording process in
2,878,888
obliterating and recording processes are stopped
just as the tape loop has completed the tran
sient recording cycle.
It is the nature of gas tetrode I32 to “?re” and
become conducting upon application of positive
potential to its control grid I56 but not to “?re”
7
supply to the two trigger tubes. In the record
ing position the switch closes the plate circuit so
that the tubes may be “?red” by the transient.
In order that the tubes may be restored ‘to the
non-conducting condition before making a new
recording, the switch I26 is arranged to open the
trigger tube plate circuits when it is turned to the
playback position. This restores the contacts of
relay I05 to their original condition, removing
ti?er is interposed between the transient input 10 the blocking bias from the obliterating ampli?er
21. To prevent obliteration when this takes
terminals I9, 20 and the control grid I56. The
place, a switch blade I25 is located in the plate
transient signal is applied through blocking con
circuit of obliterating ampli?er tube 91 to open
denser I46 to grid I40 of dual triode tube I34 con
this circuit during playback.
nected as a phase inverter of conventional de
sign. The plates I36 and I43 are coupled through
Reproducing circuit detail-Fig. 6
blocking condensers 20I and 202 to grids I39 and
upon application of a negative potential. To in
sure operation of the trigger at the proper time
for transients of either polarity, a full wave rec
After the transient signal modulates the car
I42 of the dual triode I35 which is connected as
rier current and is recorded on the tape I0, and
a full wave biased detector. The plates I31 and
after the trigger circuit has operated to stop fur
MI are connected to power supply P1. The grids
I39 and I42 are both biased to cut off through 20 ther recording and further obliteration, the tran
sient signal, a facsimile of which is recorded on
the connection of grid resistors I I2, II 3 to a neg
the tape, is “played back” from the tape to an
ative bias tap on power supp-1y P1. Due to the
oscilloscope II or other indicating device by
large negative bias no plate cathode current
means
of the playback circuit. Repeated repro
?ows in tube I35 so that there is no voltage drop
duction of the transient on the indicating in
across cathode resistor I66.
strument will give an observer sufficient time to
When a transient occurs either grid I39 or I42
see the transient even though it originally was a
becomes less negative causing plate current to
very rapid one.
?ow in its section of the tube. This current pro
For the reproduction of the transient, the mag
duces a voltage drop across resistor I66 which in
turn “?res” trigger tube I32. As explained be SI) netic head I6, which is the recording head dur
ing the recording process, becomes a playback
fore, as soon as tube I32 “?res” a voltage is ap
head due to switch I22 connecting it to the play
plied to the time delay network I60, I6I and
back circuit through line 205. It is obvious that
after a suitable time interval the voltage of the
separate recording and playback heads may be
grid I58 rises su?iciently to “?re” tube I33, thus
energizing relays I05 and I62 which stop the : associated with the tape I0 if it is so desired.
Actuation of the switch blade I22 from terminal
obliterating and recording processes. During the
R to terminal P connects the magnetic head I6
time taken to build up a “?ring” potential at the
grid of tube I33 the transient is being recorded
on the tape loop in the form of a transient mod
ulated carrier wave and the operation of relays
to the playback circuit which consists of the
pre-ampli?er I3I, the playback ampli?er I30.
(which may be the same ampli?er as the record
ing ampli?er 30) the band pass ?lter 36. and the
demodulator and low pass ?lter 31, to the re
cording or indicating instrument II. It is ap
parent that the single ampli?er, which is here
recorded transient.
indicated by reference character 30 in the re
In order to reproduce the transient from the
cording circuit and I 30 in the reproducing cir
moving tape I0, a switchA is thrown from the
cuit, may be two separate ampli?ers if desired.
recording position R to the playback position P.
The pre-ampli?er I3I may employ a single
The switch A has six blades I2I, I22, I23, I24,
tube I10, and is coupled to the recording and
I25, and I26 as shown in Figures 4 and 5. In the
reproducing ampli?er I30 by a blocking conw
recording circuit shown in detail in Figure 4, the
denser HI and a resistor I12. The plate of the
actuation of the switch A causes blade I2I to
tube I10 is connected to power supply P1 through
break the plate supply to oscillator 26 which is
coupling resistor I69 and ?lter resistance I68.
through the choke coil 42, and causes the blade
and the screen grid I99 is connected to the power
I22 to break the connection from the recording
supply Pl through resistor I61 and is by-passed
circuit to the magnetic head I6 and make a con- to ground by a condenser 209. A ?lter and iso
nection from the magnetic head I6 to the play
lating condenser 204 by-passes to ground the
back circuit. The playback circuit may include
junction of resistors I61, I68, I69. The signal
a Dre-ampli?er indicated generally by the ref
input from the magnetic head I6 to the pre
erence character I3I, and positioned between the
magnetic head I6 and the ampli?er 30. The am 60 ampli?er I3I is through line 205 to control grid
206 in the tube I10. ‘Bias for tube I10 is pro
pli?er 30 is adapted to amplify the transient
vided by cathode resistor 208 which is by-passed
modulated carrier signal both before it is re
by condenser 2I0. The tube 86 in the ampli?er
corded on the tape I0 and while it is being played
I30 (Fig. 4) has a grid resistor I13 which, to
back from the tape. The blade I23 of switch A
gether with the resistor I12, establishes a volt
is adapted to control the input to the ampli?er
age dividing network to cause the same voltage
30. In the recording position the input to am
to be supplied to the ampli?er I30 during repro
pli?er .30 is from the modulator 29 and in play
duction as was applied to the ampli?er during
back position the input is from the pre-amplifier
the recording process. The output of the am~
I3I. The switch blade I24 is located between-the
I05 and I62 ?nally takes place to prevent oblit
eration of the recorded transient and to prevent
superimposing additional carrier signal on the
ampli?er 30 and the high pass. ?lter 3| and is "
pli?er I 30 is applied through connection I92 to ,
adapted to direct the output of the ampli?er 30
to the magnetic head I6 when it is in the re
cording position and to the band-pass ?lter 36 of
the playback circuit when it is in the playback’
position. The blade I26 is located in the plate 75
the single T-section band pass ?lter 36 which
is comprised of two series arms each having an
inductance I14 and a condenser I15, and a shunt
arm having inductance I16 and a condenser I11.
For a carrier frequency of 2000 cycles per sec
8
8,378,888
0nd and transient signal frequency components
transient signal is applied. The amplitude of
up to 500 cycles per second, the pass band of the
?lter should extend from about 1500 cycles per
second to about 2500 cycles per second.
The band pass ?lter 36 ‘is connected to the
demodulator 31 by means of a transformer I18,
the secondary winding of which is connected to
the plates of a double diode recti?er tube I19.
The output of the double diode tube I19 is con
the input transient signal can be controlled by
the potentiometer 32.
Figures '1 and 8 illustrate a type of head I6
?lter comprised of two M-derived sections I8I
and I82. There ‘are two series branches and
three shunt branches in the ?lter. The. ?rst
series branch is comprised of inductor I83 and
a condenser I 84, and the second series branch 15
reproducing circuits, and inside the coil 2“! is
a rigid pole piece M9. The movable block 2“
which is particularly useful for a transient re
cording device. It comprises a base 2I5 upon
which is mounted a stationary block M6 and a
movable block 2I1. Inside the stationary block
2I6 there is a coil 2“! which is adapted to be
nected through a resistance I80 to a low pass 10 electrically connected into the recording or the
is comprised of inductor I85 and a condenser
I86. , The ?rst shunt branch has a condenser
I81, the second shunt branch has a condenser
I88, and the third shunt branch has a condenser
I89. The output of the second section I62 of the ?lter is applied across a resistor I93 and
then to output terminals I94 and I95, to which
may be attached an oscilloscope, oscillograph, or
other indicating device lg. One of the sections
of the low pass ?lter has ts frequency of maxi
mum attenuation at the carrier frequency 2000
is attached to the base 2I5 by means of a screw
220 about which the block is adapted to pivot
to establish an open position shown in Figure 7
and a closed position shown in Figure 8. The
magnetic tape I0 is adapted to lie between the
movable block 2" and the stationary block 2I8,
and when the head I6 is in its open position may
be slipped out from between the two blocks.
This construction is particularly valuable for
transient recording devices which may be located
in a remote place such for example as a remote
power supply line. The recording device may be
connected to the line and left in an operating
condition.
If a transient should occur it will
of the carrier, 4000 cycles. Adjusting the ?lter
be recorded. For an installation of this type the
switch 41 (Fig. 2) to stop the motor I 4 is val
uable. Examination of the recording device at
In some applications the use of the internal
clip 223 is provided for latching the two blocks
2| 6 and 2H together when the head I6 is in its
cycles and the other section has its frequency
of maximum attenuation at the second harmonic
sections I8I and I82 in this manner e?‘ectively 30 a later date will disclose the presence of the re
corded transient and the tape can be removed
suppresses the carrier frequency and its second
from the head I6 and taken back to the labora
harmonic and causes only the transient signal
tory for study. A movable pole piece MI is posi
to be applied to the output terminals I94 and
tioned within the movable block 2 I 1 and is biased
I95.
toward the tape I0 by a spring 222. A spring
External trigger controL-Fig. 5
automatic trigger circuit 33 may not be desir
able. I, therefore, provide an external trigger
operating condition.
obliterating ampli?er and stopping the record
having four resistances 221, 228, 229, and 230.
Figure 9 illustrates diagrammatically a timing
circuit which may be actuated by an operator
device utilizing my invention and adapted to re
40
to effect the same results as the actuation of
cord the speed of a bullet 225. The timing device
the automatic circuit insofar as blocking the
comprises an oscillator 226 in a bridge circuit
ing process are concerned.
Switch I65 is man
ually controlled and switches the phase inverter
out of the circuit and connects grid I56 of gas
tetrode I32 to the external control circuit. The
external trigger circuit comprises a switch I96
With all four resistances in the circuit there is
no output to the recording head I6 as the bridge
circuit is balanced. The bullet 225, upon being
?red, breaks or otherwise alters the resistance
221 thereby unbalancing the bridge circuit and
which may be operated byhand or by some ex
causing signal output to the recording head I6,
ternal circuit. One terminal of the switch I96
is connected to the positive terminal I91 of a
low voltage D. C. source whose negative termi
nal is grounded, and the other terminal of the
switch is connected through switch I65 to the
control grid I56 of the ?rst gas tetrode tube I32.
'“ Resistor I98 is provided to maintain grid I56
which signal is recorded on the tape I0 in ac
cordance with my invention. The bullet then
breaks or otherwise alters the resistance 228 re
establishing a balance in the bridge circuit which
stops the recording of the signal. The recorded
transient consisting of a few cycles of a known
frequency from oscillator 226, may then be re
at ground potential until the external control
produced on an oscillograph and the time of
is actuated. Applying positive bias to the con
?ight from resistance 221 to resistance 228 de
trol grid I56 causes the tube I32 to ?re thereby
termined from the number of cycles of the signal
initiating the sequence of events which blocks
on the oscillograph and the distance d between
. the obliterating ampli?er 21 and ‘stops the mag 60 resistances 221 and 228.
netic head I6 from recording as has heretofore
The present application is directed to features
been described.
of the invention disclosed and claimed- herein
Modulation check-Fig. 6
and relating to systems and methods for studying
transient phenomena, and more particularly to
I have provided a switch 200 which connects 65 such systems and methods employing an electric
the oscilloscope II directly to the output of the
circuit for recording on a, recording medium a
ampli?er 30 in order to make it possible to ob
transient circuit condition occurring on the cir
serve-‘in the oscilloscope the amount of modu
cuit and utilizing the record of the transient for
lation for applications where the transient can
studying the characteristics of the transient by
be caused at the will of an operator, such for 70 continuously making an obliterable record of the
example as an impact welder. It is possible to
circuit conditions under study on an endlessly
regulate the amount of modulation in advance
operating cyclically-effective recording medium,
of recording a' transient to be studied on the
such as a magnetic recording medium, so that
recording medium. If there is too much or too
the circuit conditions are continuously recorded;
little modulation it can be adjusted before the 75 the continuous recording operation being accom
2,878,888
panied by a continuous obliteration‘ of the re
comings and the obliterating action being stopped
upon the occurrence of a transient condition so
as to retain on the recording medium a record
of a signal corresponding to the transient occur
rence and the recording operation being discon
tinued after the. transient occurrence has been
9
reproducibly recordable on said magnetic re
cording medium and representative of the condi
tions of said circuit; said recording medium being
cyclically operated at a predetermined rate cor
related to the frequency of said signal voltages;
recording means for continuously magnetically _
recording on said recording medium a record of
said signal voltage and obliterating means for re
turning a portion of said medium to a uniform
enable the study of the transient occurrence by
cyclically reproducing the record and utilizing 10 state of magnetization a relatively short time in
terval after a record has been made thereon;
the reproduced record for operating a cyclically
means responsive to an occurrence of a transient
operative indicating device, such as an oscillo
circuit condition on said circuit for discontinuing
scope, which presents an image corresponding to
the action Of said obliterating means on said
the reproduced signal upon each cycle of the
recording medium; such systems and methods 15 medium; means operative a time interval there
after for rendering the recording means inopera
whichrare e?ective for studying low frequency
tive so as to retain on said recording medium
and direct current transients by modulating with
a record corresponding to said transient condi
the signal which is to be recorded a source of
tion;
and reproducing means operative to cycli
carrier oscillations of a frequency which is re
cally
reproduce
the record recorded on said re
producibly recordable on the endless magnetic 20
cording medium.
recording medium, so as to provide a modulated
3. In an arrangement for recording a transient
carrier signal which is continuously recorded on
circuit condition of an electric circuit which oc
the endless recording medium and obliterated
recorded on the medium in such manner as to
immediately thereafter, the obliterating action
being stopped upon the occurrence of a tran
sient-the reproduced recorded modulated signal
curs thereon at an unpredictable instance: an
endlessly operating magnetic recording medium;
means associated with said circuit for continu
ously supplying signal voltages of a frequency
reproducibly-recordable
on said magnetic record
modulated reproduced signal corresponding to
ing medium and representative of the conditions
the transient signal which is utilized for oper
said circuit; said recording medium being cycli
ating the cyclically operative indicating device; 30 of
cally
operated at a predetermined rate correlated
and various other novel and desirable features
to
the
frequency of said signal voltages‘; record
forming part of such systems.
'
ing means for continuously magneticallyrecord
The magnetic recording systems and'methods
ing on said recording medium a record of said
utilizing a signal modulated carrier frequency
signal voltage and obliterating means for con
which is reproducibly recordable on a magnetic 35 tinuously obliterating said record; and means re_
recording medium,‘ described herein in connec-‘
sponsive to an occurrence of a transient circuit
tion with the exempli?cations of the present in
condition on said circuit for rendering said ob
vention, embody various other inventive features
literating means ineffective and for subsequently
which are claimed in my vcopending application
rendering the recording means inoperative after
Serial No. 540,667, filed June 16, 1944, as a con 40 a signal corresponding to a predetermined in
tinuation-in-part of the application Serial No.
terval of the transient condition has been re
399,909, ?led June 26, 1941.
corded on said medium.
It will be apparent to those skilled in the art
4. In an arrangement for recording a transient
that the novel principles of the ,invention dis
circuit condition of an electric circuit: an end
closed herein in connection with speci?c exem 45 lessly operating magnetic recording medium;
pli?cations thereof will suggest various other
means for continuously supplying signal voltages
modi?cations and applications of the same. It is
'of a frequency reproducibly recordable on said
accordingly desired that in construing the
magnetic recording medium and representative
breadth of the appended claims they shall not
of the conditions of said circuit; said recording .
be limited to the speci?c exempli?cations of the 50 medium being cyclically operated at a predeter
invention described herein.
mined rate correlated to the frequency of said
I claim:
signal voltages; recording means for continuously
1. In a system for recording a transient circuit
magnetically recording on said recording medium
condition which may occur in an electric circuit
a record of said signal voltage and obliterating
at an unpredictable instant and for reproducing 55 means for returning a portion of said medium
the record: an endlessly-operating cyclically-ef
to a uniform state of magnetization a relatively
fective recording medium; recording means con
short time interval after a record has been made
being modulated so as to cyclically provide a de
nected to the circuit in which a transient is ex
thereon; and means responsive to an occurrence
pected for continuously recording the circuit con
of a transient circuit condition on said circuit for
ditions; means for obliterating the recorded sig 60 discontinuing the action of said obliterating
nal; means responsive to an occurrence of a tran
means on said medium and operative a time in
sient circuit condition for rendering the obliter
ating means inoperative; means operative a time
interval thereafter for rendering the recording
terval thereafter for discontinuing the action of
said recording means on said medium.
means inoperative so as to retain on said record
ing medium a record corresponding to said tran
sient condition; and reproducing means operative
to cyclically reproduce the record recorded on
said recording medium.
5. A device for recording a transient which may
65 occur at an unpredictable instant comprising, in
combination, an endless recording medium, means
for driving said endless medium, recording means
connected to the circuit in which the transient
is expected for continuously recording the circuit
2. In a system for recording a transient circuit 70 conditions, means for obliterating the recorded
signal, and means responsive to a‘circuit tran
condition which may occur in an electric circuit
sient condition for rendering the obliterating
at an unpredictable instant and for reproducing
means
inoperative and for rendering the record
the record: an endless-operating cyclically-effec
ing means inoperative after the transient condi
tive magnetic recording medium; means for con
tinuously supplying signal voltages of a frequency 76 tion has been recorded on the recording medium.
1O
2,878,888
6. The method of visually presenting on an
oscillagraph a non-repetitive wave which com
prises the steps of: electrically recording the non
repetitive wave on an endless medium, repeatedly
reproducing said record from said medium to es
tablish a cyclic signal the frequency of which cor
responds to the rate of repetition of said record of
saidv non-repetitive wave, and controlling the os
cillograph by said cyclic signal, the rate of occur
magnetic record material, means for driving said
record material, magnetic recording means as
sociated with said record material and connected
to a circuit in which said transient is expected,
said recording means being adapted to record on
said record material a signal corresponding to the
normal and abnormal conditions of the circuit,
magnetic obliterating means continuously oblit
erating the recorded signal during normal con
, rence of said record of said non-repetitive wave 10 ditions of the circuit, means operable upon the
being su?iciently high that together with the per
occurrence of an abnormal condition for render
sistence of the observer’s eye the trace on the
oscillograph corresponding to one cycle of said
ing said obliterating means inoperative whereby
repetitive wave appears substantially s‘teady.
7. The method of visually presenting on an os
a signal corresponding to the obnormal condition
recorded on said record material is retained. and
means operable upon the occurrence of the ob
cillograph a wave of short duration which com
normal condition and after a time delay for ren
prises'the steps of: electrically recording the short
dering said recording means inoperative to pre
wave on a short endless medium, repeatedly elec
vent a. subsequent record from being superimposed
trically reproducing said record from said short
on said recorded transient signal.
endless medium to establish a cyclic signal hav— 20
12. A device for recording a transient signal
ing a frequency which equals or exceeds the rate
comprising, in combination, endless record mate
of repetition of said record of said short Wave, and
rial, means" for cyclically driving said record ma
controlling the oscillograph by said reproduced
terial, recording means associated with said rec
signal, the rate of repetition of said record of said
ord material and connected to a circuit in which
short wave being suf?ciently high that together 25 said transient is expected, said recording means
with the persistence of the observer's eye the trace
being adapted to record on said record material
established by said oscillograph appears substan
a signal corresponding to the conditions of the
tially steady.
circuit, means for continuously erasing said rec
8. A device for visually presenting on an os
ord during normal conditions of the circuit,
cillograph the wave form of a non-repetitive elec 30 switching means operable upon the occurrence
trical transient comprising; endless signal storage
of an abnormal condition for rendering said eras
ing means inoperative whereby a signal corre
sponding to the abnormal condition recorded on
said record material is retained, and switching
peatedly rotating said endless signal storage 35 means operable upon the occurrence of the ab
means at a substantially constant rate of speed,
normal condition and after a time delay of a
electrical reproducing means in association with
duration no greater than the length of time for
said signal storage means for reproducing the
one cycle of the record material for rendering
record thereon upon each rotation thereof to es
said recording means inoperative to prevent a
tablish a cyclic signal the frequency of which 40 subsequent record from being recorded on said
corresponds to the rate of repetition of said rec
record means.
ord of said non-repetitive wave, means connect
13. A device for recording a transient compris
ing said electrical reproducing means to said os
ing in combination, an endless recording medium,
cillograph for controlling the oscillograph in ac
means for cyclically driving said recording me
cordance with said cyclic signal, the rate of oc 45 dium, recording means associated with said re
currence of said record of said non-repetitive
cording medium and adapted to be connected
wave being su?iciently high that together with
to a circuit in which a transient might occur for
the persistence of the observer’s eye the trace on
recording the circuit conditions on said medium,
the oscillograph corresponding to one cycle of said
obliterating means for destroying the recorded
non-repetitive wave appears substantially steady.
record after a short time interval, means oper
means, electrical recording means in association
with said signal storage means for recording
thereon said non-repetitive wave, means for re
9. A device for visually presenting on an oscil
lograph the wave form of an electrical transient
able upon the occurrence of a transient in the
circuit for rendering said obliterating means in
of short duration comprising, endless signal stor
operative, and means operable upon the occur
rence of said transient for rendering said record
tion with said signal storage means for recording 55 ing means inoperative after a short time delay
thereon said wave form of short duration, means
14. A device as set forth in claim 13 in which
for repeatedly rotating said endless signal stor
said recording means includes a source of carrier
age means at a substantially constant rate of
current and means for modulating said carrier
speed, the period of rotation of said storage means
current by the transient.
being comparable to the duration of said electri 60
15. A device for visually presenting on an oscil
cal transient, electrical reproducing means in as
loscope the wave form of a non-repetitive elec
sociation with said signal storage means for re
trical transient comprising: endless magnetic
producing the record thereon upon each rotation
tape means, magnetic means for recording the
thereof to establish a repeating wave, means con
entire non-repetitive transient on said magnetic
necting said electrical reproducing means to said 65 tape means, means for cyclically driving said
age means, electrical recording means in associa
oscillograph for controlling the oscillograph in
accordance with said repeating wave, the rate of
occurrence of said repeating wave being suf?
ciently high that the trace on the oscillograph
appears substantially steady.
magnetic tape means, magnetic reproducing
means actuated by the record of the non-repeti
tive transient during the cyclic rotation of the
endless tape means, said magnetic reproducing
70 means controlling said oscilloscope means to re
peatedly show the transient wave form, the rate
of reproduction of the wave form being su?iciently
second long.
high, and the persistence of the screen and of the
11. A device for use in recording a transient
human eye being such that the trace on the oscil
signal comprising, in combination, an endless 75 loscope screen appears substantially steady.
10. A device as set forth in claim 9 in which
said transient of short duration is less than one
2,378,388
11
duced signals passed by said ?lter means and so
correlated to the other elements of the system
that the demodulated reproduced signals corre
'nal which can be seen on an oscilloscope unit
spond in a predetermined manner to said original
comprising, an endless magnetic tape, means for
magnetically recording the entire non-repetitive U! transient; and visual indicating means actuated
by said demodulated reproduced signals; the rate
transient on said magnetic tape, magnetic re
of the cyclical operation of the recording medi
producing means actuated by the record on the
um being correlated to the characteristics of the
magnetic tape and connected to the said oscillo
indicating means so that in response to actuation
scope unit for producing on the oscilloscope a
visual trace of said entire non-repetitive tran 10 by said demodulated reproduced signals it pro
duces a visually observable characteristic image
sient, and means for repeatedly rotating said end
of said transient signal.
less tape to cause said visual trace to repeatedly
20. In a system for reproducing a character
appear on said oscilloscope, the rate of repetition
istic image of a transient signal: an endless re
of said trace being sufliciently high, and the per
16. A device» for converting a non-repetitive
signal transient into a substantially constant sig
sistence of the screen and of the human eye 15 cording medium; means for providing a carrier
current; said recording medium being cyclically
.being such that the trace on the screen of the
oscilloscope unit appears substantially steady.
17. A device for use in recording a transient
signal comprising in combination, an endless rec
ord member, means for driving said record mem
ber, recording means associated with said record
member and connected to a circuit in which said
transient is expected, said recording means in
cluding a source of carrier current and means for
modulating said carrier current by the signal in
operated at a predetermined rate correlated to
the frequency of the carrier current; modulator
means adapted to combine said carrier current
and said transient signal and cause said signal
to modulate said carrier current and provide a
modulated signal; said modulator means being
arranged to substantially balance out the said
transient signal; recording means including
25 means for amplifying said modulated signal and
said circuit whereby said recording means re
means for recording said modulated signal on
cords continuously on said record member, ob
literating means associated with said record
member for continuously restoring said record
said recording medium; reproducing means in
cluding means for reproducing said modulated
signal from said recording means and means for
member to the condition it was in prior to record 30 amplifying said reproduced signal; said repro
ing, ?rst switching means operable upon the event
ducing means including means for demodulating
of a transient in said circuit for rendering said
said modulated signal so as to provide an image
obliterating means inoperative, and second
signal corresponding to said original transient
switching means operable upon the event of the
signal; and visual indicating means actuated by
transient in said circuit for rendering said re
said image signal; the rate of the cyclical opera
cording means inoperative.
tion of the recording medium being correlated to
18. A device as set forth in claim 17 in which
the characteristics of the indicating means so
said record member is cyclically driven and the
that in response to actuation by said demodu
second switching means operates to render the
lated reproduced signals it produces a visually
recording means inoperative after a time delay 40 observable characteristic image of said transient
which is equal to or slightly less than the time
signal.
'
for one cycle of said record member whereby the
21. In the method of recording a transient cir
transient is retained on the record member,
cuit condition which may occur at an unpredict
19. In a system for reproducing a character
able instant on an electric circuit subjected to
istic image of an electric transient signal: an 45 predetermined normal circuit conditions, the
endless recording medium; means for providing
procedure of : continuously supplying signal volt
a carrier current of a frequency reproducibly re
ages of a frequency reproducibly recordable on a
cordable on said recording medium; said record
magnetic recording-medium and representative
ing medium being cyclically operated at a pre
of the conditions of said circuit; continuously
determined rate correlated to the frequency of 50 magnetically recording on a cyclically operating
the carrier current; modulator means for caus
endless magnetic recording medium a record of
ing said signal to modulate said carrier current
said signal voltages and continuously obliterating
and providing a modulated signal; said modu
said record; stopping further obliteration of said
lator means being arranged to substantially bal
record upon the occurrence of a transient circuit
ance out the said transient signal; recording 55 condition; and stopping further recording a pre
means for recording said modulated signal on
determined time after the obliteration of the
said recording medium; said recording means in
record was stopped.
cluding means for amplifying said modulated
22. In the method of observing a transient sig
signal and ?lter means interposed in the path
nal, the procedure of: providing a carrier cur
of the ampli?ed modulated signal and designed 60 rent of a frequency reproducibly-recordable on
to pass a range of frequencies including the fre
quency of the modulated carrier current and side
a magnetic recording medium; producing a mod
ulated signal by modulating said carrier current
bands corresponding to said transient signal and
by the transient signal; recording the modulated
to restrict the} passage of other frequencies so
signal on a magnetic recording medium which is
that the signals of the passed frequency range 65 cyclically operated at a frequency correlated to
are e?ectively recorded; reproducing means in
the carrier frequency; cyclically reproducing
cluding amplifying means for reproducing said
from the recording medium the recorded modu
modulated signal from said recording medium
lated sign-a1 and demodulating the reproduced
signal; and controlling an indicating device in
and for amplifying the reproduced signal; said
reproducing means including ?lter means de-' 70 accordance with said cyclically reproduced de
signed to pass a range of frequencies including
modulated signal.
23. In the method of observing a transient sig
the frequency of the modulated carrier current
nal, the procedure of : providing a carrier cur
and side bands corresponding to said transient
rent of a frequency reproducibly-recordable on
signal and to restrict other frequencies and de
modulator means for demodulating the repro 76 a magnetic recording medium; producing a mod
12
’
‘2,378,888
ulated signal by modulating said carrier current
by the transient signal; recording the modulated
and to render, a relatively short time interval
thereafter, said reproducing means inoperative
signal on a magnetic recording medium which is
cyclically operated at a frequency correlated to
so as to retain on said medium a record of a
the carrier frequency; cyclically reproducing
from the recording medium the recorded modu
lated signal and demodulating the reproduced
signal; and controlling a trace-producing elec
tron beam by the cyclically reproduced demodu
lated signal so as to provide a visually observable
trace.
24. In the method of observing a signal, the
procedure of: providing a carrier current. of a
frequency reproducibly-recordable on a magnetic
recording medium; producing a modulated sig
nal by modulating said carrier current by the
signal; recording the modulated signal on a mag
netic. recording medium which is cyclically oper
-, ated alt-"a, frequency correlated to the carrier fre
quency; cyclically reproducing from the record
ing medium the recorded modulated signal and
demodulating the reproduced signal; and con
trolling a trace-producing electron beam by the
cyclically reproduced demodulated signal so as to
.providea visually observable trace.
‘ 25. In a system for studying a transient signal;
an endless magnetic recording medium; a source
of carrier current of a frequency reproducibly
modulated signal corresponding to the transient
signal; oscilloscope means; and reproducing
means including demodulating means associated
with said medium and interconected with said
oscilloscope means for cyclically reproducing the
signals recorded on said medium during each
entire cycle and for cyclically impressing on said
oscilloscope means unmodulated or modulated
signals corresponding to the signals reproduced
from said medium so as to indicate overmodula
tion of the carrier by comparing the recorded
and unrecorded portions of the medium.
27. In the method of recording a transient cin
cuit condition of an electric circuit, the procedure
of: continuously supplying signal voltages of a
frequency reproducibly-recordable on a magnetic
recording medium and representative of the con
ditions of said circuit; continuously magneti
cally recording on a cyclically-operating endless
magnetic medium a record of said signal volt
ages; obliterating each record element recorded
on the medium prior to the end of the cycle
during which it was recorded; stopping oblitera
tion of said record upon the occurrence of a
transient circuit condition which it is desired to
recordable on said recording medium; said mag
record; and stopping further recording a pre
I netic recording medium being cyclically operated 30 determined time after stopping the obliteration.
at a predetermined rate correlated to the fre
28. In a system for studying a transient signal:
quency of said carrier current; modulator means
an endless magnetic recording medium; a source
for causing said signal to modulate said carrier
of carrier current of a frequency reproducibly
current by said transient signal and providing a
recordable on said recording medium; said mag
correspondingly modulated signal;
recording
means for magnetically recording on said me
dium a signal corresponding to said modulated
signal; reproducing means including demodulat
ing means for cyclically reproducing from said
medium the recorded modulated signal and for
demodulating the reproduced signal so as to
cyclically provide a demodulated reproduced sig
nal corresponding to the transient signal; and
cyclically-operative indicating means cyclically
actuated by said demodulated reproduced signal
for presenting said reproduced signal upon each
cycle of said medium.
26. In a ‘system for studying a transient signal:
an endless cyclically-operating magnetic record
netic recording medium being cyclically operated
at a predetermined rate correlated to the fre
quency of said carrier current; modulator means
for causing said signal to modulate said carrier
current by said transient signal and providing a
correspondingly modulated signal;
recording
means for magnetically recording on said me
dium a signal corresponding to said modulated
signal; reproducing means including demodulat
ing means for cyclically reproducing from said
medium the recorded modulated signal and for
demodulating the reproduced signal so as to
cyclically provide a demodulated reproduced
signal corresponding to the transient signal; and
oscilloscope means cyclically actuated by said
ing medium; a source of carrier current of a 50 reproduced demodulated signal for presenting
frequency reproducibly-recordable on said me
dium; modulator means adapted to modulate
said carrier current by said transient signal for
providing a correspondingly modulated carrier
current; magnetic recording means arranged to
continuously record on said medium _a magnetic
said signal upon'each cycle of said medium, the
cyclical rate of said medium being suf?ciently
high so that a substantially steady picture of
said signal is produced on said oscilloscope.
' 29. A system as de?ned in claim 28 in which
said transient signal is a direct current signal.
signal corresponding to the said carrier current
30. A system as de?ned in claim 28 in which
and operative upon the occurrence of a transient
said carrier current has a frequency sufficiently
to record on said medium a modulated signal
low that when modulated by an alternating tran
corresponding to the said modulated carrier cur 60 sient signal the resulting upper side band is with
rent; magnetic obliterating means spaced from
in the range which can be magnetically recorded
said recording means for continuously obliterat~
and reproduced.
1
ing the recorded signal so that said endless me
31. A system as de?ned in claim 28 in which
dium always includes a short medium portion
said carrier current has a frequency su?iciently
corresponding to the space between the record 65 high that when modulated by a very low or
ing and obliterating means upon which the rec
direct current transient signal the resulting lower
ord has been obliterated and a medium portion
side band is within the range which can be mag
upon which a record has been made; means
netically recorded and reproduced.
actuated upon the occurence of a transient to
?rst render said obliterating means inoperative 70
SEMI JOSEPH BEGUN.
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