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Патент USA US2404307

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July 16, 1946-
' J. N. WHITAKER
'
2,404,301
ELECTRICAL CIRCUIT
Filed March 31. ‘1942
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INVEN'TOR
JAMES NAPOLEON WHITAKER
BY
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ATTORNEY
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July 16, 1946.
J. N. WHITAKER
2,404,307
ELECTRICAL CIRCUIT
Filed March 31. 1942
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INVENTOR
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MES Mpomw Mun/rm.
BY
-
-
5w“!
ATTORNEY
'
2,404,307
Patented July 16, 1946
UNITED STATES PATENT OFFICE
2,404,307
ELECTRICAL CIRCUIT
James Napoleon Whitaker, West Englewood, N. J .,
assignor, to Radio Corporation of America, a
corporation of Delaware
Application March 31, 1942, Serial No. 436,983
12 Claims.
1
This invention relates to electrical circuits and,
more particularly, to electrical circuits and meth
ods for converting time-modulated impulses into
amplitude variations.
(Cl. 250-20)
variation in amplitude, the magnitude of_ the
amplitude being proportional to the time duration
of the original pulses.
>
,
Further, ‘in accordance with my method, I have
provided apparatus for carrying outthe described
In many applications in electrical signalling, it ‘ :41 method of operation, utilizing thermionic tubes
is desirable to signal by means of time variation
and without requiring the ‘aid of mechanical
of a signalling current in which the current has
commutators. This is necessary in order that
the value either zero or a predetermined constant
therequisite speed of operation can be obtained
?nite value and in which the information is
transmitted by varying the time duration either 4 10 with a minimum of maintenance and freedom
- from faulty operation.
of the spaces between the pulses or the duration
Accordingly, it isthe main object-of my inven
of the pulses themselves or a combination of vari
tion to provide a-new'_;method_ andapparatus for
ation of space and marking interval. At the
- converting i time-modulated; I pulses into ampli
same time it is desired to utilize the received en
currents: I ~
ergy in the form of amplitude variations. For 15 tude-modulated
Another object .‘of rmyi invention lisgto, provide a ‘
example, in facsimile transmissionover. long dis
' method'of converting impulseswhosetimedura
tances, in order to overcome the e?ects of fading
tion varies into a continuous unidirectional cur
it is desirable to use the constant frequencyivari
able dot type oitransmission such as is exempli
rent
'As'till
whosefurther»
amplitude
object
varies-continuously.
{,Qf} any ‘invention , is to
?ed by the Shore et 91. Patent 2,083,245. 0n the .20 provide ‘apparatus embodying a thermionic com
other hand, for recording the transmitted picture ' mutator for‘ convertingja: series;of;}pu1ses into a
it is desired to have a continuous variation. be
tween the signals vrepresentative of white to black
so that the received‘picture appears to have con
unilateral current'whosezmagnitude is propor
tional to‘the time'duration-of the received pulses.
Another object ‘of ‘my invention is to provide
tinuous tones rather than a screenpattemfsuch 25 apparatus suitable to produceimproved pictures
as the recording of CFVD dots give. --'The reason
from received CFVD signals‘. ‘- .w '_ .
for this is that where the pictures transmitted
Another object of 'my' invention will become
and received are to be used in printed reproduc
apparent to those skilled in the artupon reading
tion the picture is ordinarily screenediagain by
the photoengraver. The double screening’ipro 30 the following detailed description in connection
with the'drawings.
;
duces a moiré e?ect which is very disturbing to
In the drawings, I have shown in Figure 1 a
the observer. Moreover, this effect tends to re
duce the amount‘ of detail in the picture. Other
examples will be immediately obvious,-as, for ex
schematic sketch embodying a mechanical com
mutator to illustrate the principles of my method
ample, in measuring systems where it is’desi'red 35 arid apparatus, and have shown in Figures 2a,
to have continuous recording'graphs rather than
the broken line graph furnished bytime-modu
lated signals.
.
i
'
'
2b, 20 representative graphs of the received cur
’ rents and output~currents,~while in Fig. 3 I have
' shown in considerable detail an electrical circuit
diagram showing the commutator, limiters, key
Accordingly, by my invention, :1 provide a
method and apparatus which will convert the 40 ers, selectors, such as are utilized in my appa
' 'ratus.
time-modulated signals into amplitude-modu
Turning now to Figure‘ 1, I have shown a signal
lated signals or into signals .of a'unidiréctional
vrectifier I03 having terminals ' IIJI across which
current whose amplitude varies with time. - In ac
the signalling currents in the form of A. C. im
cordance with my invention the incoming pulse
The input current at the
signals are..utilized to derive a charge whose 45 pulses are applied.
the form MI, as shown in Fig
'
terminals
IIII
has
magnitude’ isv proportional to the timeduration ‘ ure 2a. The output of the signal recti?er I03
of the pulse. The stored charge is thereafter uti
will have the form I43 shown in Figure
lized to control v‘the amplitude of a continuous - thereafter
2b. The outputs of these signals are fed through
unidirectional current such that the amplitude
the brush I01 to the commutator I05 comprising
of the current is proportional to the stored 50 three segments I23, I25, I21,‘ separated by suit
charge. Thereafter the stored charge is dissi
able insulation I29, I3I, I33, respectively. A cen
pated. During the time the stored charge is con
tering ring H9 is grounded and provides a com
trolling the amplitude of the output current a
mon terminal point for the three storage con
.(secondimpulse is being used to produce a second
densers H3, I I 5, I II. The recti?ed impulse is con
j stored charge, and when the ?rst stored charge is 55 sequently stored-up in the condenser H3 during
being dissipated, a third pulse is used to derive
the time the segnient I23 is under the brush III'I.
a stored charge while the second stored charge is
During the time the charge is being stored by the
used to control the amplitude of the output cur
condenser I I3' the previously stored charge of
rent. These cyclic steps are thereafter repeated.
The output current therefore has a step by step 60 condenser I15 serves to actuate the recorder IZI
2,404,307
3
through the brush I09, the magnitude of the
recording current being proportional ,to the stored
charge ,of the rcondenser II5. .Atthesametime,
the charge, which had'been stored on condenser
II'I previous to the storing of the charge on the
condenser H5, is discharged to ground by way
of a brush I I I. As the commutator I05 continues
.to rotate the condenser H3 comes under the
brush I09 to control the magnitude of the 're—
corder current, while condenser H5 is discharged
through the brush I I I and condenser vI I'I receives
'a new charge corresponding to the duration of
the second pulse received and the operation is
cyclically repeated during the transmission of the
~picture. The recorder HI will have a recording
current whose form is that shown as I45 v:i-n Fig
‘ure 2C. It will be ‘readily appreciated that the
use of mechanical commutator-s ‘is not wholly de
sirablein ‘View of the -fact that --it ‘limits the-speed
of operation and, in addition, requires constant
attendance in order to avoid improper operation
due to accumulation of dirt under the brushes, as
well as the difficulties introduced by changes in
‘leakage path of the insulating members. Accord
ingly, ‘I have provided a thermionic equivalent in -
Figure 3 of the circuit shown :in Figure 1 for pur
poses of illustrating the method of pperation of
‘my invention, which equivalent is substantially
of any speed limitations vand which requires a
minimum of supervision in operation.
In Figure 3 I have ‘indicated by means of hori
zontal dotted lines three channels A, B, C, and
by vertical dotted ‘lines the component parts of ‘
each of the channels in order to simplify the ‘un
4
scribed in the Shumard Patent 2,146,862, as well
as the article entitled “Some Electronic Switch
,ing Circuits” in the May 1938 issue of “Electrical
Engineering,” at page ‘209 through page 220.
Consequently, a detailed explanation of the op
eration of the commutator circuit will not be
given, since these circuits are already well known.
It is merely necessary to point out that the op
eration of the commutator is such that, assum
ing channel C ‘is operating, the tube VT3 is pass
ing current, while tubes VTZ and VTI are cut off.
‘Upon the arrival of the second impulse tube VT3
is cut oil and VTZis actuated. Upon the arrival
of the third impulse tube VTZ is cut oil and VTI
is actuated, and the cycle repeats. In this fash
ion the commutator is synchronized ‘with the in
coming signals.
Assuming that a pulse from VTZB has actuated
the tube VT3 so that it conducts, a positive ‘pulse
‘from the tube VT3 is applied to the input grid I75
of the limiter tube ‘VT6 over a conductor "I16 and
a grid resistor I'TI, the pulse being derived from
"the drop across the cathode resistor R9.
As a
result, plate current ‘in the tube VT6 ?ows
through the resistor RI 6 producing an IR. drop
which causes the grid vI18 of the second half of
the tube VT6 to become negative with respect to
its cathode. The negative potential on this grid
blocks the ?ow of plate current in the second ‘half
of the tube VT6, reducing the IRdrop across the
resistor RZI to zero. This permits the push-pull
stage tube 'VT9 to act as an ampli?er for the in
coming signal, which is applied over conductors
ml to the grids I84 and I85 of tube VTQ through
derstanding of the operation of ‘the circuit. The 35 the input transformer TR3, since the cut-.o?- bias
component parts of'each of the channels com
prises'acommutator, a limiter, a push-pull ,keyer,
obtained from across the resistor RZI has been
removed.
'
an output selector including a storage circuit, a
This removal vof ‘the out 01f bias occurs since
discharge tube’, an output selector, and an out
the grid I18 of the second section of the tube
‘put tube. These 'parts are identified onFig. .3 of 40 VT6 is negative at this stage of the operation
the drawings ‘between the ‘vertical dotted lines.
with respect .to its cathode as stated above.
The operation of channel C will ‘be described
The ampli?ed signal is applied to the storage
in detail and the mode of operation of {channels
circuit comprising the ‘tube 'VTIZ and the con
A and B will be readily understood as each nf'the
denser vCIZ through the transformer TRG. The.
channels A, ‘B, and C operates in a similar ‘ recti?er tube VTIZ permits current to flow in
manner.
,only one direction and consequently the con
The input signals are consequently fed to the
denser CI-Z will begin to charge ‘up. ‘The storage
three push-pull keyers 'VT'I, VTB, and VT?)
of .the charge continues as long as the signal vpulse
through the transformers TRI, TR2, .‘I‘R3, .as well
is applied. It is to be noted that the capacity
as to the recti?er-ampli?er tube 'VT23 actuating = of the condenser CI2 is made sufficiently large
the trigger tube VT25 of a commutator indicated
so as to prevent its charging beyond ‘the linear
in its entirety ‘by reference character I59 com
portion of the charging characteristic during the
prising the three tubes'VTI,‘VT2,"VT3. The tubes
operating cycle. The discharge tube ‘VTI 5 is pre
'VTI, VTZ, ‘W3, and VT25 are gas :tubes, and as
vented from operating by the IR .drop across the
shown ‘in both the patent and the publication 1' resistor RIB in channel A which is applied over
a channel cross connection I88 and the output
tube V'I‘ZI is held inoperative by the plate cur
rent drawn vby the tube VTI8 through the re:
sistor R24 which reduces the screen voltage on
transformer I58, functions in the manner .of a
the screen grid I89 of the tube VTZI ‘below the
conventional full wave detector of radio or other
point at which plate current can ?ow.
carrier signals, such for example as the detector
The grid I90 of 'the'tube VTI8 is connected
mentioned below, they may, for example, be RCA
885-tubes.
The rectifying portion of the tube VT23, which
is fed from the input terminals I5I through the
I0 ‘of Fig. 1. The signals applied to the termi
nals I 5I ‘may be signals I4I of Fig. 2a of ‘.the
drawings. These signals, after recti?cation, are
applied to the grid 116! .of the amplifying portion
of VT23. The plate Iii-2 of the'latter is connected
to a plate supply source SI by way of the usual
load resistor Hi3. A coupling condenser I54 cou
ples the ampli?ed output .of the tube VT23 to the ‘
grid I65 of the tube VT25 which serves as a trig
lger tube for the electronic commutator I60. The
control pulses .for the commutator I60 are fur
nished to the commutator over .a conductor I61.
to RI 5 in channel‘B over a channel cross connect
ing conductor I9I and therefore is positive with
respect to the cathode as long as channel B is
vnot operative. As a result, a charge is being
stored up in condenser C_I2. At the same time
the grid I92 of the tube "YTH in channel B is
no ‘longer biased'by the drop in R2] over a chan
nelcross connection I94 so that plate current will
flow if there isany charge on condenser CII .in
channel B, and consequently, the charge of .con
denser II in channelB will be dissipated or dis
The 60111111111313!‘ is of the Shumayd type ,de- 75 charged by the tube VTIII so that the condenser
2,404,307
.
=5
6
ception this length of time will be governed by
CII will be ready to receive a new charge upon
the length of the transmitted dot with the com
the arrival of the second impulse.
mutator synchronized at the dot frequency).
The grid I92 ‘of the discharge tube VTI4 in
channel B is connected to the resistor RZI in
channel 0 over the channel cross connection I94
and‘therefore is at zero potential with respect
todts cathode when channel C is receiving a
triggering or control impulse. At the same time
the ouput tube VTI9 of channel A is in an opera
tive condition and will draw a plate current in 10
After one storage circuit has received its charge,
the push-pull keyer in that particular channel is
rendered inoperative by the action of the com
mutator and the next channel is made operative _
at the same time over one of the channel cross
connecting conductors I94, 204, or I88, with the
output tube in the ?rst channel becoming oper
ative by virtue of one of the cross-connections
proportion to the amount‘ofcharge appearing
20I, I9I, or 2H! between the commutator limiter
across the condenser CIO of channel A. VTIS
of the second channel and the output selector of
operates because the selector tube VTIB of chan
the ?rst channel.
nel Av is vnot drawing plate current due to the
When the storage circuit of the second channel
‘fact that its control grid I98 is connected over 15
has
received its charge, and the output tube in
a cross channel connection 20I to the resistor RI 8
the ?rst channel has done its work, the push-pull
of channel C which applies a negative bias (or a
keyer in the second channel is‘ rendered inoper
lesspositive bias) to the grid I98 of VTIS of chan
ative along with the push-pull keyer tube in the
nel A. The screen grid I96_ of the output tube
V_TI9_ in channel A is connected to the plates of 20 ?rst channel. Control of the push-pull keyer
tubes VT‘I, VTB, and VT9 is provided by the re
the tube VTIG which, at times, draw' plate cur
sistors
RIB, R20, and R2I in the plate circuits
rentlthrough theload resistor R22. When the
of the tubes VT4, VT5, and VTG as explained
channel C is cut oil, the ?ow of plate current
above. The output tube in the second channel is
"in‘the tube VTIQ reduces the screen voltage on
permitted
to operate by virtue of the fact that
25
the screen grid ‘I90 of the tube VTI9 below the
the
selector
tube of the second channel iszcross- '
vpoint where. plate current can flow. The screen
connected to the commutator-limiter‘ ‘of the third
grid 206 ofgthe output‘tube VT20 in channel B
channel.
'is connectedto the plates of,the tube VTI'I.
When channel _A is ,cut on‘, a bias is applied to
These cross connections as indicated '
previously are 2| 0,’ HI, and 2M. The output tube
‘the grids 201 of the; tubeVTI'I over a channel 30 of the ?rst channel is. rendered inoperative be
cause of the cross-connection between the ?rst
Tcross connecting‘ conductor _2_I0. When channel
channel output selector and the second channel
'A'is cut, on‘, the ?ow?piplate current reduces the
commutator-limiter. The charge stored in the
screen voltage on'the screen grid 206 of the tube
storage circuit of the ?rst-channel is dissipated
V120 ,belowthe point whereplate current can
in a discharge tube in the storage system because
'?ow. ‘It will be,noted therefore that the fol 35 the
grid of the discharge tube is cross-connected
'lowing ‘functions "are , performed simultaneously.
to the output of the commutator-limiter system
"The storage ‘circuit: in'.channe1 C is receiving a
of the third channel. These cross, connections
charge from‘ the'incoming, signal. The storage
circuit in channel B 'is being cleared for a new
‘charge, and theoutput tube of channel A is oper
ating; jdrawing platecurrent in proportion to the
are designated I88, 204, and I94 and are con
40 nected to the grids 2 I6, H8, and I92 of the tubes
VTI 5, VTI3, and VTI4 respectively. The amount
of current appearing in each output tube is de
circuit of condenser CIO of the storage system
pendent upon the magnitude of the charge built
in channel A. ' As soon as the commutator shifts
up in the storage circuit which, in turn, is de
to the nextiposition, which is channel B, the
pendent upon the time duration of the signal
45
following action takes place. VT9 of channel 0
during the charge period. Thus a, complete cycle
is rendered inoperative due to the IR drop across
is set up which continues as long as signals are
'the resistor R2I.. The tube VTIII is rendered
fed to the input terminals I'5I.
inoperative by a bias' applied to its grid I92, over
The output current is obtained from the output
VTIB is rendered inoperative over the conduc 50 terminals I53 and they operate any suitable re
corder, such as is known in the prior art, which
tor .I9I because of the reduced IR drop across
may for example be a light valve or a pyro re
the resistor RI5. The tube V'I‘ZI is permitted
corder. It willbe appreciated that other types
to operate because there is no IR drop across
of tubes may be used without going outside the
the resistor 24 due to‘ the flow of plate current
in the tube ,VTIB, and, ?nally, the tube VTI3 65 scope of my invention, and, of course, other modi
the conductor-‘I94 for the same reason. The tube
_. dissipates the. charge across the condenser CID.
The tube VTI3 is rendered operative for this
purpose over a channel cross connecting con
?cations of the circuits which I have shown will
immediately suggest themselves to those skilled
in the art, and therefore it is desired-that the
disclosure be construed as covering all forms of
ductor 204 which is connected to the resistor
R20. Thus, the action continues throughout each 60 converting systems which fallclearly within the
spirit and scope of the hereinafter appended
.cycle. of operation so that when one channel is
claims.
.
receiving a charge the charge of the following
Various alterations and modi?cations of the
. channel is being dissipated, while the output tube
present invention may become apparent to those
in the previous channel is operating. The com
mutator switching is substantially instantaneous 65 skilled in theart and it is desirable that any and
all such modi?cations and alterations be consid
(less than 0.1 micro-second) , leaving’ no space or
ered within the purview of the present invention
overlap between channels so that the output is
except as limited by the hereinafter appended
substantially continuous and of an amplitude pro
portional to the signal.‘
' _It will thus be perceived that the commutator 70
system operates each‘ channel separately, permit
ting each storage circuit to receive ‘a charge, the
amplitude of which will be proportional to the ‘
length of time,a_,signa1 is being passed by the
push-pull keyer stage (in CFVD picture signal re
9
claims.
‘
‘
Having now described my invention, what I
claim is:
"
.
1. The method of converting time-modulated
signals into amplitude-modulated signals which
comprises the steps of receiving time-modulated
signals, deriving an electrical charge proportional
2,404,307
7
put current by only one of the said control means.
8. An electrical circuit for converting time
to the time duration of the signals, and utilizing
the derived charge to control the amplitude of a
modulated signals into amplitude-modulated sig
unidirectional current in proportion to the magni
tude of the derived charge.
2. The method of converting time-modulated
nals which comprises means for supplying time
modulated signals to a plurality of amplifying
channels, means for deriving a charge propor
tional to the time duration of the signals con—
signals into amplitude-modulated .signals which
comprises the steps of receiving time-modulated
signals, deriving an electrical charge proportional
nected in each of the said amplifying channels,
means to control the amplitude of a unidirec
to the time duration of the signals, utilizing the
derived charge to control the amplitude of a unl~ 10 tional current by the said derived charge con
nected to each of the channels, commutator
directional current in proportion to the magni
means
to sequentially and cyclically select each
tude of the derived charge, and thereafter dis
of the control means to control the amplitude of
sipating the derived charge.
the output current by only one of the said con
3. The method of converting time-modulated
trol
means, and means to dissipate one of the
15
signals into amplitude-modulated signals which
derived charges.
comprises the steps of receiving time-modulated
9. An electrical circuit for converting time
signals, deriving an electrical charge proportional
to the time duration of the signals, utilizing the
derived charge to control the amplitude of a uni—
directional current in proportion to the magni
tude of the derived charge, thereafter dissipating
modulated signals into amplitude-modulated sig
nals which comprises means for receiving time
20 modulated signals, means for deriving an electri
cal charge proportional to the time duration of
the signals, means for utilizing the derived charge
the derived charge, simultaneously deriving a sec
ond charge from a signal following the ?rst signal
to control the amplitude of a unidirectional cur
rent in proportion to the magnitude of the de
rived charge, means for thereafter dissipating the
unidirectional current by a charge derived from 25 derived charge, means for simultaneously deriv
a signal preceding the ?rst signal and cyclically
ing a second charge from a signal following the
repeating the aforesaid steps.
?rst signal, means for concurrently controlling
4. An electrical circuit for converting time
the amplitude of the unidirectional current by
modulated signals ‘into amplitude-modulated sig
a charge derived from a signal preceding the ?rst
30
nals which comprises means for receiving time
signal, means for cyclically repeating the afore
modulated signals, means for deriving an elec
said steps, and means operated by the received
trical charge proportional to the time duration of
signals to control the initiation of the cyclic repe
the signals, and means for utilizing the derived
tition.
charge to control the amplitude of a unidirec
10. An electrical circuit for converting time
tional current in proportion to the magnitude of 35 modulated signals into amplitude-modulated sig
the derived charge.
'
nals which comprises means for supplying time
5. An electrical circuit for converting time
modulated signals to a plurality of amplifying
and concurrently controlling the amplitude of the
modulated signals into amplitude-modulated sig
nals which comprises means for receiving time
modulated signals, means for deriving an elec
channels, means for deriving a charge propor
40 tional to the time duration of the signals con
trical charge proportional to the time duration of
the signals, means for utilizing the derived charge
to control the amplitude of a unidirectional cur
rent in proportion to the magnitude of the de
rived charge, and means for thereafter dissipat- ‘
ing the derived charge,
6. An electrical circuit for converting time
modulated signals into amplitude-modulated sig
nals which comprises means for receiving time
modulated signals, means for deriving an elec
trical charge proportional to the time duration of
the signals, means for utilizing the derived charge
to control the amplitude of a unidirectional cur
rent in proportion to the magnitude of the de- ‘
rived charge, means for thereafter dissipating the '
derived charge, means for simultaneously de
riving a second charge from a signal following
the ?rst signal, means for concurrently control
ling the amplitude of the unidirectional current
by a charge derived from a signal preceding the
?rst signal, and means for cyclically repeating the
aforesaid steps.
7. An electrical circuit for converting time
modulated signals into amplitude~modulated sig
nals which comprises means for supplying time
modulated signals to a plurality of amplifying
channels, means for deriving a charge propor
tional to the time duration of the signals con
nected in each of the said amplifying channels,
nected in each of the said amplifying channels,
means to control the amplitude of a unidirec
tional current by the said derived charge con
nected to each of the channels, and commutator
means synchronized by the supplied signals to se
quentially and cyclically select each .of the control
means to control the amplitude of the output cur
rent by only one of the said control’ means.
11. An electrical circuit for converting time
modulated signals into amplitude-modulated sig
nals which comprises means for supplying time
modulated signals to a plurality of amplifying
channels, means for deriving a charge propor
tional to the time duration of the signals con
nected in each of the said amplifying channels,
means to control the amplitude of a unidirec
tional current by the said derived charge con
nected to each of the channels, commutator
means to sequentially and cyclically select each
of the control means to control the amplitude of
the output current by only one of the said control
means, means to dissipate one of the derived
charges, and synchronizing means controlled by
the supplied signals to regulate the period of said
65 commutator means.
12. An electrical circuit for converting time
modulated signals recurring at predetermined
time intervals into amplitude-modulated signals
which comprises means for deriving an electrical
charge proportional to the time duration of the
means to control the amplitude of a unidirectional
signals during each time interval of a signal, and
current by the said derived charge connected to
means for controlling the amplitude of a unidi
rectional current in proportion to the magnitude
each of the channels, and commutator means to
of. the derived charge.
sequentially and cyclically select each of the con
JAMES N. WHITAKER.
trol means to control the amplitude of the out 75
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