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Патент USA US3045087

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July 17, 1952
R. MATTHEWS ETAL
3,045,071
ELECTRICAL TRANSMISSION AND STORAGE OF INFORMATION
REPRESENTED BY DIRECT VOLTAGES
Filed Nov. l2, 1957
6 Sheets-Sheet 1
INI/ENTORÄ
July 17, 1962
R. MATTHEWS ETAL
3,045,071
ELECTRICAL TR ANSMISSION AND STORAGE OF INFORMA TIoN
REPRESENTED BY DIRECT VOLTAGES
Filed Nov. l2, 1957
6 Sheets-Sheet 2
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INVENTOÍYS
J“IY 17, 1962
R. MATTHEWS ETAL
3,045,071
ELECTRICAL TRANSMISSION AND STORAGE OF INFORMATION
REPRESENTEO BY DIRECT VOLTAGES
Filed Nov. 12, 1957
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INVENTO/ï S
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July 17,"1962
R. MATTHEWS ETAL
3,045 ,071
ELECTRICAL TRANSMISSION AND STORAGE OF‘ I NFoRMATIoN
REPRESENTED BY DIRECT VOLTAGES
Filed Nov. l2, 1957
July 17, 1962
R. MATTHEWS ETAL
3,045,071 A
ELECTRICAL TRANSMISSION AND STORAGE OF INFORMATION
REPRESENTED BY DIRECT VOL TAGES
Filed Nov. l2, 1957
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R. MATTHEWS ETAL
3,045,071
ELECTRICAL TRANSMISSION AND STORAGE OF INFORMATION
REPRESENTED BY DIRECT VOLTAGES
Filed NOV. 12, 1957
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3,045,071
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Patented July 17, 1962
1
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the voltage level to be transmitted. At the receiver there
‘
3,045,071 '
are provided means -responsive to the frequency of `the
ELECTRICAL TRANSMISSION AND STORAGE 0F
received signals to recouvert the signa-ls to a direct voltage
INFORMATION REPRESENTED BY DIRECT
dependent on the frequency. With this Iarrangement the
VOLTAGES
Robert Matthews and James Stewart Johnston, London, 5 voltage to be transmitted is represented by a frequency
England, assignors to Decca Limited, a British company
and, except for transient conditions when a change in
Filed Nov. 12, 1957, Ser. No. 695,730 ,
the transmitted frequency occurs, the transmission line or
Claims priority, application Great Britain Nov. 13, 1956
other transmission circuit cannot introduce any change
14 Claims. (Cl. 179-15)
in the transmitted frequency, and hence cannot `affect
10 the transmission of the information. Although a saw
This invention relates to the transmission and storage
tooth signal is generated, the infomation is conveyed by
of information represented by direct voltages.
the frequency of its signal and `hence any distortion of
~It will be 'appreciated that, if direct voltages are to be
the waveform by the transmission circuit is immaterial.
Iaccurately reproduced at «a distant point, they cannot
_ In fact, as explained later, it may be desirable to change
simply be transmitted over a transmission line as D.C. 15 the waveform before it is transmitted. The aforemen
signals or as amplitude modulations on a carrier since
tioned predetermined rate of rise of the saw-tooth signal
the transmission path will introduce attenuation and hence
is preferably linear to facilitate the accurate conversion
change the magnitude of the signals. Thus a transmission
of the frequency into a corresponding direct voltage at
system for the distant transmission of direct voltages
the receiver but it will be apparent that non-linear wave
must convert these voltages into signals which are not 20 forms might be used if the receiver is arranged accord
affected by the transmission line and it is one of the ob
ingly. Most @conveniently the comparator means `are ar
jects of the present invention to provide an improved
ranged to cut off and fre-start the saw-tooth generator
transmission system for this purpose which can be used
when the compared voltages lare equal.
for the yaccurate transmission of information represented
The actual frequencies employed are determined by
by direct voltages over transmission circuits such as are 25 the rate of rise of the saw-too-th signal and, by suitable
used yfor speech transmission. Similar considerations ap
choice of the rate, the range of frequencies to be trans
ply -to the recording of such information and it is a fur
mitted can be chosen as required. These frequencies may
ther object of the present invention to provide means for
readily be yarranged Ito lie in an audio frequency range so
recording information conveyed by such direct voltage
that the signals can be -transmitted over speech circuits.
signals so that they can be `accurately reproduced.
30 Conveniently for this purpose the reproduction frequen
According to this invention »apparatus for converting
cies are »arranged to lie between ‘300 and 3000 cycles per
information represented by a direct Voltage of varying
second.
magnitude into an alternating voltage having a frequency
'Phe aforementioned saw~tooth generator may comprise
representative of the amplitude of the direct voltage com
prises a saw-tooth generator -for producing a saw-tooth
signal the amplitude of which increases from Ka datum at
a high gain ampliñer with -a capacitive feedback connec
tion from the output to the input and a resistive input
circuit which is connected to a source of reference volt
a predetermined rate and comparator means arranged to
age whereby the ‘amplifier with its feedback and input
compare Ithe voltage to be converted with the saw-tooth
generator output voltage and to cut-off land »re-start the -
saw-tooth generator when the compared voltages are in
predetermined relationship, whereby the saw-tooth gen
erator produces -a saw-tooth output having a repetition fre
quency `dependent on the voltage level to be converted.
From the saw-tooth output, there may be derived a sinus
oidal or substantially sinusoidal output of a frequency
dependent on (eg. equal to or a muliple of) the saw
tooth frequency. Conveniently the saw-tooth output is
used to produce a rectangular waveform which is subse
quently filtered toprovide a sinusoidal outputy of double
the saw-tooth frequency. Such output signals can be
transmitted over transmission lines or they can be re
corded and, since the information is conveyed by the
frequencyof the signals, any waveform distortion in the
transmission or recording will not ‘affect the laccuracy of
the information. 'I'he `original direct voltage signals may
be reproduced from these output signals by means re
sponsive to the -frequency of the received signals arranged
to reconvert thesignals to a direct voltage dependent on
the frequency.
40
circuits forms a Miller integrator producing la linear saw*
tooth voltage output rising lat a rate proportional to the
applied reference voltage.
For many transmission line circuits, for example if
telephone speech circuits ‘are employed, it is desirable to
eliminate or reduce the higher frequencies so as to mini
mise lthe possibility of cross talk. Similarly in recording
signals, the recording apparatus may have only a limited
frequency range and it maybe desirable to avoid «applying
the higher frequency signals to the recording apparatus.
For these reasons the output of the saw-tooth generator
is preferably converted into a substantially sinusoidal
form. One means for doing this comprises circuit means
arranged tto produce a trigger impulse from each saw
t-ooth wave, a bi-stable multivibrator producing rectangu
lar Waveform output pulses, means for applying said trig
ger impulses to> said bi-stable multivibrator «and a low
pass filter connected to said bi-stable multivibrator for
producing a substantially sinusoidal waveform the fre
quency which is half the saw-tooth repetition frequency.
The circuit means for producing la trigger impulse may
conveniently comprise la monostable ñip~flop triggered`
In applying this invention to the transmission of in 60 by the output of said comparator and `the trigger impulse
formation represented by Ádirect voltages, apparatus for
produced by this nip-dop may be used to cut-off and
transmitting information represented by a direct voltage of
re-start the saw-tooth generator «as vwell as to trigger said
varying magnitude may comprise a saw-tooth generator
lai-stable multivibrator.
.
for producing »a saw-tooth signal the amplitudeof which
As previously indicated, the «apparatus of the present
increases from a datum at a predetermined rate land com
parator means arrange-d» to compare the voltage to be
transmitted with the saw~tooth Igenerator output voltage
and to cut-off and re-start the saw-tooth generator when
the compared voltages »are in ¿a predetermined relation
ship, whereby the saw-tooth generator Vproduces a Ysaw
tooth output having` a repetition frequency dependent on
invention may also be used in combination with record
ing means for recording the alternating voltage out-put
and thus it is possible to provide a record representative
of direct voltage levels. The record-ing may conveniently
70 be effected on magnetic tape by means of a magnetic
tape recorder since the alternating frequencies can be ar
ranged to `be within the audio range. It will be'readily
3,045,071
3
output rising at a rate proportional to the applied refer
»apparent however `that such alternating signals may be
ence volt-age.
recorded on other .forms of recording media. To repro
The aforementioned shaping circuit may comprise a
squarer -to recouvert the input signals into a rectangular
duce the direct voltage levels there may be provided play
back means for reproducing the recorded alternating volt
ages and means responsive to the frequency of the re
produced signals to reconvert the signals to the direct volt
age dependent upon the frequency.
If the recording is effected on a medium, such as mag
netic tape, which is mechanically traversed past a repro
ducing head, to ensure correct reproduction of the fre 10
quencies recorded and hence `of the direct voltage input
levels, a synchronising signal may be recorded on the me
dium. This synchronising signal might be of a standard
reference frequency, for example a 50 cycles per second
alternating mains supply frequency recorded on a sepa
waveform, a first self-timing monost-able flip-flop triggered
by the leading or trailing edge of the rectangular wave
form Ato produce »a short duration pulse for controlling the
pulse sampling demodulator and a second self-timing
monostable ñip-ñop triggered by the trailing edge of .the
output pulse of the first flip-flop for cutting olf and re
starting 4the integrator.
The information transmitting system described above
. may readily be used for multi-channel operation either
on a frequency-sharing or_on a time-sharing basis. In
15 the former case, a frequency range may be allocated for
each channel and band pass ñlters used at the receiver
to separate the incoming signals into the separate chan
` -r-ate recording channel on the medium or it might be a
readily identifiable signal in a multiplex channel. As an
example of the latter arrangement, if the normal range
of voltages to be recorded was i5() volts and n such
signals were to be recorded, the recording system might 20
be arranged to »record n+1 channels, the extra channel
being representative of a predetermined voltage level,
nels. If time-sharing multi-channel operation lis required,
sequential switching »at low frequency may ‘be effected in
synchronism at the transmission and receiving stations,
forex-ample, Iby using a «mains electricity supply if syn
chronised mains are available at 4the two stations, or by
a low frequency synchronising signal -transmitted over the
transmitting system. One method of effecting simul
e.g. +60 volts, so that this last channel would provide
both synchronisation and a reference llevel. Thus, if for
taneous commutation at the receiver and .the transmitter
example the recording med-ium was magnetic tape and 25 .is
-by the use of gas-filled count-ing tubes such as are
the ltape was played back at the wrong speed, this last
known under ‘the name “Dekatron” to effect switching
channel would enable the correct voltage level to be
established.
At a receiver for reconverting to a direct voltage the
alternating voltage signals (e.g., the signals transmitted
from channel Ito channel in synchronism. If such tubes
are used, to ensure the appropriate channel is selected, a
30 resetting signal which may, for example, be a signal out
over a line or reproduced signals reproduced from a re
cording), .there may be provided yan integrator producing
a saw-tooth Waveform the amplitude of which increases
from a datum at a predetermined rate, means for con
side thc normal range used for signalling (and hence trans
mitted as a frequency outside the normal frequency range
and separable by filters from the other signals) may be
sent from the transmitting station to Ithe receiving sta
trolling the saw-tooth repetition frequency in accordance 35 tion and, after separation from the other signals, applied
as a re-setting pulse to a particular cathode of the tube.
with «the frequency of the -alternating input signals and
Such a re-setting pulse would be sent out once in each
circuit means providing an outpu-t representative of the
cycle of operation of the cathodes of the counting tube
peak voltage of the integrator output. ln one arrange
ment, a receiver comprises a shaping circuit for convert
ing the receiver input signals into repetitive pulses syn
chronised with the frequency of the input signals, an
integrator producing a saw-tooth waveform the amplitude
to put the counting tube back into step if, for any rea
son, it should have gone out of step.
Similarly a number of direct voltages may =be recorded
on a single recording medium, for example a single mag
netic track by frequency multiplexing or time-multiplex
ing in a similar way to that described above for transmit
switch means for said integrator controlled by the repeti
ting information about a number of voltages over a single
tive pulses so that said -integrator produces waveforms
increasing to a potential dependent on the tfrequency of 45 communication circuit.
The apparatus of the present invention has particular
the input signals, and a pulse sampling dernodulator pro
application to the transmission and recording of inter
viding an output representative of the peak voltage of
of which increases from a datum at a predetermined rate,
the integrator output.
If the direct voltages are to be
reproduced linearly proportional to the input direct volt
ages at the transmitter, lthe integrator must produce -a saw
tooth waveform` similar to that provided by the saw-tooth
generator at the transmitter »and most conveniently linear
waveforms are employed at the receiver as vvell as at the
scan markers in a radar display system employing inter
scan markers of the kind described in United States Patent
No. 2,849,708, granted August 26, 1958. In that speci
íication there is described »an interscan marker system in
which the directions and starting positions of the markers
are controlled by direct voltages and hence, by recording
these direct voltages the positions of the interscan markers
transmitter.
The invention also includes within its scope apparatus 55 may be recorded. These interscan markers may, for ex
ample, be tracking markers manually adjusted, possibly
for converting alternating voltage input signals of a vary
with rate-aiding, to follow the position of a ltarget in
ing frequency into a direct voltage of a magnitude repre
radar display, or they may be automatically controlled
sentative of the frequency of 4the input signal comprising
to follow the position of a target as, for example, in the
a shaping circuit for converting the input `signals into
manner described in co-pending United States Specifica
repetitive pulses synchronised with the frequency of the
tion No. 678,890, tiled August 19, 1957. Such interscan
»input signals, an integrator producing a saw-tooth wave
form the amplitude of which increases from a datum at
a predetermined rate, switch means for said integrator
markers may be used, Iwhen made to follow targets on
nected to a source of reference voltage whereby this
iliary display.
a radar display, Ito transfer the »target position informa
tion and also possibly other information to an auxiliary
controlled by the repetitive pulses so -that the integrator
produces waveforms increasing to a potential dependent 65 display showing selected information and, in such a case,
the apparatus of ‘the present invention permits of this in
on the frequency of the linput signals, and a pulse sampling
formation :being transmitted to a remote display or of a
deinodulator providing an output representative of the
permanent record being made of the information with
peak voltage -of the integrator output.
out requiring «any extra operation other than the neces
The aforementioned integrator may comprise a high
gain amplifier with a capacitive feedback connection from 70 sary manual or automatic varying of a track marker
which is required for putting the information on 4the aux
the output to the input and a resistive input circuit con
In the following description reference will 4be made to
reference voltage :is applied to the amplifier input so that
the accompanying drawings in which:
the amplifier with its feedback and input circuits forms
a Miller integrator producing a linear saw-tooth voltage 75 FIGURE 1 is a diagram illustrating a transmitting ap
3,045,071
paratus for converting a direct voltage of varying magni
tude into alternating voltages of a frequency representa
tive of the magnitude of the direct voltage;
FIGURE 2 is an explanatory waveform diagram;
FIGURE 3 is a diagram illustrating a receiving appa
ratus for reconverting the signals from the Vsystem of
FIGURE 1 into direct voltages;
,
t
FIGURE 4 is a simplified circuit diagram of one part
of the apparatus of FIGURE 3;
FIGURE 5 is a block diagram illustrating a frequency
multiplex transmitting and receiving system for trans
mitting information about a plurality of direct voltages;
FIGURES 6A and 6B taken together are a diagram
illustrating a time multiplex system for transmitting and
remotely displayingV information labout a plurality of in
terscan markers on a radar plan position indicator;
VFIGURE 7 is a Waveform diagram; and
v
FIGURES 8 and 9 are diagrams illustrating parts of
` a synchronising system.
6
ranged to produce an output voltage in an output circuit
25 as soon as the saw-tooth voltage exceeds the applied
input voltage and this output voltage is fed to a mono
R
u
stable self-timing iiip-flop circuit 26 which produces a
short duration impulse used for re-setting the saw-tooth
voitage generator by controlling the switches 20, 21.
The output of the saw-tooth generator is thus of the
form shown in FIGURE 2 in which there is a sloping
waveform 36 having a slope controlled by the reference
Voltage applied to the input resistor 16. This slope is
rapidly terminated as indicated at 31 when the saw-tooth
is re-set. T'here is then a short interval 32 before the
start of the next saw-tooth impulsepthisinterval corre
sponding to the duration of the re-setting impulse from
the iiip-iiop.
This interval is made as short as possible
ibut, as will be explained later, compensation for this in
terval can be effected at the receiver so that it does not
aäect the accuracy of the system.
It will be seen that,
neglecting this short interval 32, the saw-tooth waveform
FIGURE 1 illustrates an apparatus for converting a 20 has a duration which is directly proportional tothe volt
direct voltage of varying magnitude into an outputV signal
age applied to the input terminal 10 and thus the repeti
having a frequency representative of the magnitude of
tion frequency of the sawtooth output is proportional to
the direct voltage. The voltage to be converted, which
this applied voltage. Since the saw-tooth generator is
for convenience is considered as a voltage rwith respect to
1re-setas soon as the flip-flop 26 is operated, the output
earth, is applied to an input terminal 11i which is con 25 of the comparator 11 comprises relatively short dura
The
tion pulses of thesame repetition frequency as the saw
other input to this voltage comparator, which is de
tooth waveform output.
he output of the iiip-ñop 26
scribed below, is taken from the output circuit 12 of a
has thisV same repetition frequency andis used to provide
nected to one input of a voltage comparator 11.
saw-tooth voltage generator 13. This saw-tooth voltage
generator comprises a high gain amplifier 14 having a' »
feedback capacitor 15 and a feedback resistor 16. As
sociated with the capacitive feedback circuit 1.5 is an input
resistor 17 and associated with the resistor yfeedback cir
cuit 16 is an input resistor 18. The two feedback cir
cuits are permanently connected to the output of ampli
tier 14 and to the aforementioned output circuit 12. The
input 19 Ito the amplifier is switchably connected by
means of an electronic switch 2i? to either
the feedback capacitor 15 and the input
the junction of the feedback resistor 16
resistor 18. The switch 20 is operated
the junction of
resistor 17 or
and the input
simultaneously
with a second electronic vswitch .21 which serves to earth
the input side of the capacitor 15 `when the switch 2li
connects the input to the amplifier to the junction of re
t sisters 16, 18. When the switch 20 is set so that the feed
back and input circuit comprising capacitor 1S and re
sistor 17 is operative, the amplifier operates a Miller in
tegrator to generate a linear saw-tooth voltage having a
the required output signals. For this purpose the short
duration impulses from the iiip-iiop 26 are fed to a bi
stable multivibrator 33, e.g. an Eccles-Jordan circuit,
giving rectangular waveform output pulses having a pulse
duration half the pulse repetition period, this 'bi-stable
multivibrator 33 being set in one condition by one im
pulse from the flip-nop 26 and set in the other condition
by the next successive impulse. These output pulses
from the bi-sta-ble Vmultivibrator 33 are passed through
a loW pass filter 34 to provide an output of substantially
sinusoidal Waveform. This waveform may lthen be ap
plied to a transmission line as an alternating-voltage with
out any direct voltage component, for example by means
‘of a transformer 35 feeding the output from the filter
34 to a transmission line 36.
If it is desired to record
the output pulses they may be fed from the transformer
35 to a recorder, e.g. a magnetic tape recorder, and in
FIGURE 1 there is illustrated diagrammatically a switch
ing device 37 for feeding the output from the trans
former 35 either to a recorder 38 or to the transmission
very high degree of linearity provided the amplifier 14
line 36 for transmitting the output to a distant point. It
has a high gain.v This saw-tooth voltage starts'from the 50 will be understood that if desired the recorder might be
level -to which the capacitor 15 has previously been
operated . -at the same time as the signals are being
charged. This level is determined by the voltage ap
transmitted.
` plied to the input resistor 118 when the switch is in the
other condition in which condition the amplifier 14 with
resistors 16, 18 acts as a see-saw circuit so that the po
tential at the output circuit 12, and hence the potential
to which the capacitor 15 is charged, varies as the poten
i tial applied to the input resistor 18 but in the opposite
direction, the ratio of the input and output potentials
being equal to the ratio of the magnitudes of the input
and feedback resistors 18 and 16. VIn thearrangement of
the present invention, constant direct voltages are applied
to the input resistors 17 and >18, so that the integrator 13
produces a saw-tooth waveform‘having a fixed slope and
The frequency of Vthe output signals is determined by
the repetition rate of the saw-tooth generator and, since
the slope of the Waveform is determined, inter alia, by
the voltage applied to the input resistor 17, it is readily
l possible by suitable choice of this voltage to adjust the
saw-tooth generator to give output signals of »any desired
band of repetition frequencies for any required range of
input voltages. The apparatus is preferably arranged so
that the output frequencies are in the audio frequency
band, for example, ina band of 300 to 3000 cycles per
second. Such signals may very conveniently be Vtrans
-rnitted over telephone speech circuits and may readily be
starting from a fixed datum level.
65 recorded using a magnetic tape recorder.
The comparator 11 is arranged to produce an output
FIGURE 3 illustrates a receiverfor reconverting the
pulse when the saw-tooth waveform level is equal to the
alternating voltage output from the apparatus of FIGURE
voltage applied to the input terminal 10. This compara
l into direct voltages having a magnitude dependent on
tor may comprise, for example, two grid-controlled `valves Y the frequency of
alternating voltage. In FIGURE 3
having their cathodes connected to a common cathode 70 there is illustratedthe
diagrammatically
an input transformer
load of high impedances to form what is known as a
“long-tailed pair”; the two Ivoltages to be compared are . 4@ which can be connected by means of a switch 41 either
to a transmission line 42 for receiving signals direct from
applied respectively to the control grids of the two valves
one or other of which will conduct according to which
has the Yhigher grid voltage. The comparator is ar
a transmitter such as that shown in FIGURE 1 or to a
reproducer 43 for reproducing signals recorded by a
'recorder suchvas the recorder 38 in FIGURE l.. The out
3,945,071
7
before the peak of each saw-tooth wave and these output
pulses switch the pulse sampling demodulator so that the
put from the trans-former 40 is fed through a low pass
filter 44 to a variable gain amplifier 45 and thence into a
squarer 46 which converts the substantially sinusoidal
input resistor 69 and feedback resistor 66 are connected
into circuit thereby causing the voltage level in the output
circuit 67 rapidly toV become representative of the instan
output of the ampliñer 45 into a rectangular Waveform.
This squarer might consist simply of a limiting circuit
limiting both the positive and negative going excursions
taneous level of the saw-tooth voltage.
of the signal voltage so as to produce a substantially rec
tangular waveform; if the limiting were symmetrical about
acts as a Miller integrator with zero rate of change of
the mean voltage level, the output would be a square
output voltage so thereby holding this output voltage
waveform having substantial unity mark to space ratio
but this is not essential since the principal purpose of
until the next sampling pulse.
(or negative-going) edge present in the waveform once
but only one in each cycle. Alternately this squarer 46
might comprise a circuit such as is shown diagram
to a source of reference potential illustrated as a tap on
a potentiometer S5.
With this arrangement, when the
'
Since the slope of the saw-tooth waveform from the
generator 76 and the datum level for the starting of the
waveform are constants determined by vthe reference
voltages applied to the two input circuits of the saw-tooth
the squarer is to ensure that there is a steep positive-going
matically in FIGURE 4 comprising two grid-controlled
valves 50 and 51 having their cathodes connected together
with a common cathode impedance S2 of high magnitude
to form a “long-tailed pair.” The anode circuits of the
valves 50, 51 include load resistors 53, 54 respectively
and the input signal is applied to the control grid of the
valve 50. The control grid of the valve 51 is connected
At the end of
each sampling pulse the switches 68, 71 revert to connect
the feedback capacitor 64 into circuit so that the amplifier
generator 76, the output voltage sampled by the pulse
sampling demodulator 63 is thus representative of the
duration of the saw-tooth waveform and hence is de
pendent on the frequency of the incoming signals. If
this frequency should change, the output voltage from the
demo'dulator 63 will immediately follow such a change
since it is dependent< on the duration of each separate
Y saw-tooth waveform. By suitably choosing the duration
of the impulses from the flip-liop 75 to correspond to the
alternating voltage input signal potential exceeds that
duration of the impulses from the Hip-flop 26 in the
transmitter of FIGURE l, taking account of the fact that
the saw-tooth waveform frequency at the receiver is twice
that at the transmitter, the effect of the short intervals
32 (FIGURE 2) in the saw-tooth waveforms at the trans
_the grid of the valve 51, the valve 50 will be cut-off. Thus
mitter and receiver are cancelled. However, the duration
30
square waves are developed at the anodes of the valves
of these impulses may be made so short that the effect
50 and 51 and the output may be taken from either of
of these intervals in any case may be negligible.
these two anodes, for example by means of an output
It will be seen that the receiver of FIGURE 3 produces
circuit 56 connected to the anode of valve 511, to give a
on the grid of valve 51 determined by the setting of the
potentiometer 55, the valve 5d will conduct heavily whilst,
when the input signal potential is below the potential on
rectangular pulse waveform. If the potentiometer 55 is
adjusted so that the potential applied to the grid of the
valve 51 is the mean potential of the alternating input
signals applied to the grid ofthe valve 50, then this wave
form will have a unity 4mark to space ratio.
This rec
tangular waveform is applied to a self-timing monostable
ñip-ñop circuit 60 (FIGURE 3) vwhich produces short
duration output pulses in two output circuits 61, 62,
Van output direct voltage which corresponds to the input
direct voltage at the transmitter. The ratio of the mag
nitudes of these voltages may be adjusted if necessary
by adjusting the reference potential controlling the wave
form slopes of the saw-tooth generators 13 and 76. A
signal representative of a fixed direct voltage input may
be transmitted periodically to enable the reference volt
ages at these saw-tooth generators in the transmitter and
these pulses loccurring once in each cycle 'of the rectangu
lar waveform at a point where the voltage changes rapidly.
The pulses in the circuit 61 are fed as control signals to
a pulse sampling demodulator 63 which comprises a high
receiver to be set so that the output voltage is exactly
gain ampliiier 64 having a ñrst feedback circuit formed
the equipment merely by altering the reference potentials.
The information transmitting system described above
by a capacitor `65 and a second feedback circuit formed
by a resistor 66 .which feedback circuits are both per
manently connected to the amplifier output 67. An
electronic switch 68 connects the amplifier input alter
natively either to the junction of the feedback resistor
66 and an input resistor 69 or to the feedback capacitor
65. The switch 68 is ganged with a second electronic
switch 71 for earthing the input end of 'the capacitor 65
when the feedback resistor 66 is operative and the two
electronic switches 68, 71 are controlled by the pulses
from the output circuit 61 of the flip-flop 60 so that for
'a short period once in each cycle of the alteranting volt
age input to the receiver the resistive feedback and re
sistive input circuits are connected to the input to the
receiver.
The output circuit 62 from the Hip-flop 6G is connected
to a second monostable self-timing flip-hop 7S which is
triggered by the trailing edge of the output from the
ñip-flop 60 and which produces short duration impulses.
These impulses are applied as switching impulses to a saw
tooth generator 76, which is similar in construction to
the saw-tooth generator 13 of FIGURE l, and the im
pulses thus serve to re-set the saw-tooth generator peri
odically at the frequency of the alternating voltage input `
signals to the receiver. The output waveform of the saw
tooth generator 76 is thus similar to that illustrated in
FIGURE 2 and this output is applied to the aforemen
tioned input resistor 69 of the pulse sampling demodulator
63. lThe output pulses from the flip-flop 60 occur just
equal to the input voltage.Y
It is thus possible to reproduce at the receiver the di
rect voltages applied to the transmitter. Positive or nega
tive voltages may be transmitted without modification of
may be used for multi-channel operation either on a fre
quency-sharing or on a time-sharing basis. A frequency
multiplex system is illustrated diagrammatically in FIG
URE 5 in which there are shown four input channels, 80,
81, 82, 83 carrying direct voltages to be transmitted.
These four voltages are fed respectively to four trans
mitters 84, 85, 86, 87 each of which is similar to the trans
mitting device illustrated in FIGURE l and produces a
sinusoidal output signal having a frequency representative
of the level of the direct voltage input. The reference po
tentials of the saw-tooth generators of the four transmit
ters are adjusted, however, so that the output signals lie
in separate frequency bands. These signals may then be
fed over the transmission circuit 88 and subsequently sep
arated by four band-pass filters 89, 90, 91, 92 and fed re
spectively to four separate receivers 93, 94, 95, 96 which
may each be similar to the receiver illustrated in FIGURE
3 and which feed respectively four output channels 97, 93,
99, 10i). Thus the four receivers will reproduce the four
direct voltage inputs in the four output channels 97-100.
The frequency multiplexing arrangement of FIGURE 5
can also be used in a system in which the signals from
the transmitters are recorded and are subsequently repro
duced provided the recording equipment has a bandwidth
sufficient to accommodate the full frequency range ern
ployed by all the transmitters.
As previously indicated, multi-channel operation can
3,045,071
` 9
10
also be etïected by using a time-sharing system‘and FIG
URES 6A and 6B illustrate diagrammatically one such
ed a source of alternating current 150. This may be an
oscillator but very conveniently is an alternating current
system arranged for transmitting and reproducing four
direct voltages representative of the positions of interscan
mains supply. This alternating current serves as a fre
quency standard for the switching of the electronic switch
marker traces occurring between radar traces on a radar
142 at the transmitting apparatus and also, as described
plan position indicator. Such interscan markers are cle-v
below, as a frequency standard for a corresponding switch
scribed and claimed in United States Patent No. 2,849,
in the receiver. In the transmitter the output of the oscil
708, granted August 26, 1958. Referring to FIGURE 6A
lator
is fed to a drive circuit 151 for providing drive im
. vthere is illustrated diagrammatically a pulse radar system
pulses for a gas ñlled counting tube 152 which may con
comprising `a transmitter 110 arranged to produce short 10 veniently
be the type of tube known yunder the name
duration radio frequency pulses of a microwave frequency
“Deka-tron.” Such a tube has a plurality of cathodes and,
under the control of a synchronising pulse generator 111.
by the application of two drive pulses, a discharge can be
These pulses from the transmitter 110 are fed through a
re-set from one cathode to the next. The tube can thus Ibe
duplexer 112 to a directional scanning antenna 113 which
used to eiîect a number of circuit connections in sequence
is rotated in bearing by means of a drive motor 114. 15 at a rate controlled by input signals from the alternating
Echoes of these transmitted pulses reñected from distant
current source 159. The various cathodes of the count
targets, atfer being received by the antenna 113, are fed
ing tube 152 are arranged to control in succession lfour
through the duplexer 11=2 to a receiver `115 and thence to
bi~stable multivibrator circuits 153 to l156 (conveniently
a detector and video amplifier stage 116 to provide video
Eccles-Jordan circuits) which produce, in succession,
output signals which are applied as a brightness modula 20 square
wave signals for effecting the necessary switching
tion -to a cathode ray plan position indicator display tube
of the electronic switch 142.
y
117. This display tube has iixed orthogonal detlector
The output from the terminal 149 will thus consist
means, e.g. deilector coils, and the deñections of the cath
ode ray fbeam in two orthogonal directions are controlled
of a sequence of groups of alternating current signals,
the frequencies of the various groups corresponding to
respectively lby two sweep generators 118, 119 producing 25 the
direct voltages on the input leads 140 and these
saw-tooth deflection signals synchronised with the output
groups occurring in sequence in synchronism with the
of the synchronising pulse generator 111 and having
switching under the control of the alternating current
slopes controlled in accordance with the sine and cosine of
source
150. This output from ythe terminal 149 is illus
the angular position of the antenna 1‘13 by means of a
bearing resolver 12,0 rotated in synchronism with the 30 trated in FIGURE 6B as being fed by means of a trans
mission line 169 to a receiver 161 for converting these
antenna. The arrangementV thus far described constitutes
alternating currents into direct voltages. This receiver
a known type of pulse radar apparatus having a plan posi
comprises a low-pass ñlter 162 feeding a variable gain
tion display. This plan position indicator display also
amplifier 163 the output of which is applied to a squar
has marker traces produced by deñection of the cathode
ing circuit 164 which triggers a flip-‘lop 165. This ilip
rayv beam during the intervals between the radar display
flop produces short duration impulses of which the trail
scans -by means of interscan signal waveform generators
ing edge triggers a further flip-Hop 166 producing short
13u, 131 associated respectively with the two orthogonal
duration output impulses for cutting off and re-starting
defiector means. As previously mentioned, such an in
a saw-tooth generator 167. The components 162 to
terscan marker system is 1described in United States Patent
167 respectively correspond to the components 44, 45,
No.'2.,849,708, granted August 26, 1958. The .interscan
46, 60, 75 and 76 of FIGURE 3 and therefore will not
be described in further detail. It will be recollected that
in FIGURE 3 the first dip-flop had also an output cir
tooth generators 1.3 of FIGURE 1 having two direct voltcuit for controlling a pulse samplingdemodulator. In
age inputs which control respectively the rate of scan and
Vthe datum level from which the scan starts. The direct 45 the arrangement of FIGURE 6B, an output from the
ilip-tlop 165 is fed to distributor 163, which may be an
voltage input circuits for the two interscan waveform gen
electronic switching device and which serves to feed the
erators 130, 131 are shown a-t 132,> 133, 134, 13'5 in FIG
impulses from the ñip-flop 165 to four circuits 169 to
marker waveform generators -may conveniently each com
prise a waveform generating circuit similar to the saw
URE 6A. The present invention is concerned more par
ticularly with the transmissionl of these voltages to a re
mote point and is not concernedIwith the production of
172 in succession under the control of switching im
pulses. These switching impulses are illustrated as be
50 ing derived from the alternating current sources 150 at
these voltages. KVThesevol-tages may, for example, be ar
the transmitter by means of a line 173 which feeds this
ranged to cause a` -marlier trace to follow automatically
alternating current to a drive circuit 174 for a gas iilled
the position of a selected target as, for example, is de
counting tube 175 which may conveniently be a “Deka
scribed in co-pending United States speciñcation No.
tron” tube. This tube 165 controls the sequential opera
678,890, tiled August 19., 1957.
`
tion of four bi-stable multivibrators 176 to 179 (con
The vfour direct voltages to be transmitted are red re
veniently Eccles-Jordan circuits) providing the necessary
spectively by means of four leads 140 to a transmitting
unit 141. In this transmitting unitl the four voltages are
bedescribed later, switches the four voltages in sequence
' gating waveforms for the distributor 168. If an alternat
ing current mains supply is used as the source 150 and
ifV the transmitter and receiver operate on synchronised
are’pe'r'iodically> cut-oiï¿ and re-started by a monostable
65 pulses which are switched in sequence over the four leads
applied to an electronic switch 142 which, in a method to
to a circuit 143V feeding a voltage comparator 144. This 60 main supply sources, it will be appreciated that there is
no need for any line 173 between the transmitter and
`voltage comparator can be` similar to the voltage com
receiver as the transmitter and receiver may each make
e parator 11 in FIGURE 1 and compares the applied volt
use of the alternating current main supply to provide the
age from one of theV leads 140 with the output froma saw
necessary synchronisation of the switching. The im
ltooth generator» 145. of which the saw-tooth waveforms
ilipfñop 146. The lflip-Hop is tiiggered by the output of '
q the comparator 144. The output from this ñip-ilop is also
used to ltrigger a square wave generator 147 to. produce
»
a square wave output which is fed through a low-,pass ñlter
70
148 to an output terminal 149. The saw-tooth generator
_145, ñip-ilop` 14,6, square wave generator 147` and` low
169 to 172 are fed by these four leads respectively to
four pulse sampling demodulators 180i to 183 which may
be similar to the pulse sampling demodulator 63 of FIG
URE 3 and which each serve in sequence to sample the
output waveform from the saw-tooth generator 167.
These demodulators might be arranged directly to sam
the output waveform from the saw-tooth generator
naSS. filter 14% may be, Ȕdenticaliwith the corresponding - ple
167 but, in the arrangement of FIGURE 6B, there is
units 13, 2,6, 33 and 34` of FIGURE l. For controlling
provided a fast pulse sampling demodulator 184, which
theV operation of the electrical switch 142 there is provid 75 may
be similar to the pulse sampling demodulator 63 of
3,045,071
11
URE 7. FIGURE 9 illustrates a method of employing '
FIGURE 3 and which samples the output from the saw
this waveform at the receiver differing from that described.
tooth generator 167 directly under the control of the sam
In FIGURE 9 which is a diagram illustrating a modi
pling pulse from the ñip-ilop 165 to provide a direct
ñcation of part of the receiver of FIGURE 6B the out
voltage output which will change its level in accordance
with the frequencies in each group of the alternating in Ul put from the fast pulse sampling demodulator 184 is fed
to a comparator 220 which compares the output volt
put signals to the receiver. The four pulse sampling
age sampled by the demodulator 184 with that derived
demodulators 180 to 183 are then arranged Vto sample
from a reference source indicated diagrammatically by
the output from the demodulator 184. By providing this
a potentiometer 221 and produces an output signal when
extra demodulator 184, the demodulators 180 to 183
output from the demodulator 184 and hence the saw
can be arranged to sample the output only during the
tooth voltage exceeds the level of the reference voltage
middle of each group of saw-tooth waveforms by suitable
from potentiometer 221. This reference voltage is set
timing of the waveforms produced by the bi-stable multi
so that only the synchronising signals 200 of FIGURE 7
vibrators 176 to 179. The demodulators 180-183 need
would cause any output from the comparator 220. This
not therefore be synchronised to sample every saw-tooth
output from the comparator 220 is fed as a re-setting im
waveform but only each group of waveforms thereby
pulse of the counting tube 175. Such an arrangement
avoiding any possibility of erroneous outputs being ob
may be used where an alternating current mains supply
tained due to faulty synchronisation causing sampling by
is used as the source for synchronising the switching at
one of the demodulators of a saw-tooth waveform belong
the transmitter and the distribution at the receiver. In
ing to either a previous or a following group. It will be
seen that the demodulators 180 to 183 will provide four 20 FIGURE 9, however, there is illustrated diagrammatical
ly a double triode valve arranged as a resistance-capacity
separate direct voltage outputs corresponding to the four
alternating input voltages applied to the transmitter over
leads 140. These outputs are illustrated as being applied
to interscan drive circuits 190, 191 connected to the
coupled variable frequency oscillator which is tuned by
192. The interscan drive circuits 19t), 191 may be
similar to the units 130, 131 in the radar apparatus and
thus the display tube 192 will display interscan markers
corresponding to those on the display tube 117 of the
ly since the construction of such an oscillator is well
known. The output from the comparator 220 is fed as
synchronising pulses to this oscillator to lock the fre
quency of the oscillator to the frequency of the alternat
30 ing current at the transmitting end. A similar oscilla
a variable resistor 223 to oscillate approximately in syn
chronism with the frequency of the source at the trans
. orthogonal deflector means of a display cathode ray tube 25
radar apparatus.
If desired automatic control means may be provided
for ensuring that the electronic switch 142 and the dis
tributor 168 operate in synchronism to switch the ap
propriate signals to the appropriate channels. In one ar
rangement for this purpose, a direct voltage signal out
side the normal amplitude range of the required signals to
be transmitted and which would therefore be transmit
ted as a frequency outside the normal frequency range,
may be sent from the transmitting station to the receiv
ing station. Since this synchronising signal is outside the
normal frequency range it is separable by filters from
the other signals and, after such separation at the receiver,
may be applied as a re-setting pulse to a particular cath
ode of the counting tube 175 at the receiver. Such a re
setting pulse may be sent out once in each cycle of opera
tion of the cathodes of the counting tube to put the count
ing tube back into step if, for any reason, it should have
got out of step. FIGURE 7 illustrates one example of
the multiplex waveform from a saw-tooth generator which
might be used for this purpose. It will be seen that the
saw-tooth signals occur in groups having amplitudes and
hence frequencies corresponding to ñve different levels
of direct voltage input. The lowest frequency group of
signals, that is to say the signals having the maximum
mitter. This oscillator is illustrated only diagrammatical
tor, apart from the synchronising circuit may convenient
ly be used at the transmitter if an oscillator is required
as the source of alternating current for controlling the
switching. Such synchronising of a local oscillator at
the receiver by a comparator can only be effective to an
accuracy of the time interval corresponding to one of the
saw-tooth waveformsv 200 of FIGURE 7. This time in
terval is greater than the duration of the saw-tooth wave
forms representative of the required direct voltages and
40 hence errors of a saw-tooth cycle of the required signals
may occur but any such small errors do not affect the
output signals since the fast pulse-sampling demodulator
184 in the receiver permits sampling to be effected to
give the separate outputs in the centre of each group of
saw-tooth waveforms.
We claim:
1. Apparatus for recording and reproducing informa
tion represented by a direct voltage of varying magnitudes
comprising a sawtooth generator arranged, on application
of a control signal, to produce a sawtooth signal the am
plitude of which increases from a datum `at a- predeter
mined rate, comparator means coupled to said sawtooth
generator to compare the voltage to be converted with
the sawtooth generator output voltage and to produce a
amplitude, which are illustrated as saw-tooth waveforms 55 control signal when the compared voltages are in a pre
determined relationship, means for applying said control
200, may be used as the synchronising signals whilst the
signal to said sawtooth generator to cut-off and re-start
other saw-tooth signals illustrated typically by the four
said sawtooth generator when a control signal is produced,
different waveforms 201, 202, 20?», 204 provide the four
means for converting the sawtooth output of the sawtooth
different direct voltage levels to be transmitted. Such a
waveform may be produced as illustrated in FIGURE 8 60 generator in to a substantially sinusoidal waveform, a re
corder for recording the converted sawtooth output, a re
which is a diagram illustrating a modification of part of
producer for reproducing the recorded signals, and a vre
the transmitting equipment of FIGURE 6A. In FIG
ceiver coupled to said reproducer and having means re
URE 8 there are four input leads 140 to the electronic
sponsive to the frequency of the input signals to the re
switch 142 as before and also a fifth input lead 210 which
ceiver to re-convert these signals to a direct voltage de
is connected to a source of reference potential indicat
pendent on the frequency of the input signals.
ed diagrammatically by potentiometer 211 which provides
a reference potential greater than the maximum am
plitudes of any of the four direct voltages to be trans
mitted. The switching sequence of the switch 142 is
controlled by ñve bi-stable multivibrators, that is to say
the four mutlivibrators 153 to 156 of FIGURE 6A and
a fifth multivibrator 212 under the control of the count
ing tube 152. The output from the electronic switch may
then be fed to the comparator 144 exactly as in FIGURE
2. Apparatus for converting information represented
by a direct voltage of varying magnitude into an alternat
ing voltage having a frequency representative of the am
plitude of the direct voltage comprising a saw-tooth gen
erator arranged, on application of a control signal, to pro
duce a saw-tooth signal the amplitude of which increases
from a datum at a pre-determined rate, comparator means
coupledrto said saw-tooth generator to compare the volt
6A to produce the required Waveform illustrated in FIG 75 age to beV converted with the saw-tooth generator output
$045,071
voltage and to produce a control signal when the com- i
pared voltages are in a pre-determined relationship, means
14
trol signal to produce a sinusoidal waveform of a fre
quency proportional to the repetition -frequency of the
for applying said control signal Ito said saW-toothgenera
sawtooth waveform.
'
tor to cut-off and re-start said saw-tooth generator when a
8. Apparatus for converting information represented
control signal is produced, and means, including a -low
by a direct voltage of varying magnitude into an alter
pass iilter, responsive to said control signal to produce a
nating voltage having a frequency representative of the
sinusoidal waveform of Ia frequency proportional to .the
amplitude of the direct voltage comprising a high gain
repetition frequency of said sawtooth output, a transmis
amplifier with a capacitive feedback connection from the
sion circuit to which the variable frequency output of said
amplifier output to the 4amplifier _input and a resistive
saw-tooth generator is fed, and a receiver connected to 10
input circuit, a source of reference voltage connected to
said ltransmission circuit to receive the Variable frequency
said resistive input whereby the ampliiier'forms a linear
signals and having means responsive to the frequency of
saw-tooth generator producing a saw-tooth signal the am
the input signals to the receiver to re-convert these signals
plitude of which increases from a datum at a rate de
to a direct voltage dependent on the frequency of input
signals.
`
'
'
pendent on said reference voltage, a control circuit for
`
15 stopping and re-starting the saw-tooth output of said am
3. Apparatus -as claimed in claim 2 wherein said re
plifier on application of a control signal, comparator
means coupled to said amplifier output to compare the
ceiver comprises an integrator producing a sawtooth
waveform the amplitude of which increases from a datum
voltage to be converted with the 4amplifier output voltage
at a predetermined rate, means for controlling «the saw
and to produce said control signal when the compared
tooth repetition frequency in accordance with the fre
quency o_f the alternating input signals and circuit means
providing an output representative of the peak voltage
0f the integrator output. ’
voltages are in a pre-determined relationship, means cou
pling said comparator circuit to said control circuit to
apply said control signal to said amplifier, and means, in
cluding a «low-pass iilter, responsive to said control signal
i
4. Apparatus asrclaimed in claim 2 wherein said re
produce a sinusoidal waveform of a frequency propor
ceiver comprises a shaping> circuit for converting the re 25 to
tional tothe repetition frequency of said sawtooth output.
ceiver input signals yintorepetitive >pulses synchronised
9. Apparatus for converting information represented
with the frequency of the input signals, an integrator pro
by a direct voltage of varying magnitude into »an alter
ducing a saw-tooth waveform the amplitude of which in
nating voltage having a frequency representative of the
yamplitude of the `direct voltage comprising a saw-tooth
creases from a datum at a predetermined rate, switch
means for said integrator controlled by the repetitive
pulses so that said integrator produces waveforms increas
ing to a potential dependent on the frequency of the input
signals and a pulse sampling demodulator providing an
30 generator arranged, on application of a control signal, to
produce a saw-tooth signal the amplitude of which in
output representative of the peak voltage of the integrator `
output.
5. Apparatus for converting an alternating voltage in
put signal of a varying frequency into a direct voltage cf
a magnitude »representative of the `frequency of the input
signal comprising a shaping circuit for converting the
input -signal into repetitive pulses synchronised With the
frequency of the input signal, an integrator producing a
saw-tooth Waveform the »amplitude of which increases
`from a datum at a predetermined rate, switch means for
creases from a datum at a pre-determined rate, compara
tor means coupled to said saw-tooth generator to compare
the voltage to be converted with the saw-tooth generator
35 output voltage «and to produce -a control signal when the
compared voltages are in a pre-determined relationship,
means for applying said control signal to said saw-tooth
generator to cut-olf and -re-start said saw-tooth generator
when a control signal is produced, a lui-stable multivibra
tor arranged to produce rectangular waveform output
pulses, means for Iapplying said control signals to said
multivibrator to lsynchronize the rectangular waveform
output with said control pulses, and a low-pass filter con
said integrator controlled by the repetitive pulses to cut
nected to said Ybi-stable multivibrator for producing a sub
off and re-start the integrator in response to each of said 45 stantially sinusoidal waveform of frequency which is haflf
pulses so that the integrator produces waveforms synchro
nized with said repetitive pulses `and increasing to a po
tential dependent on the frequency of the input signal,
the saw-tooth repetition frequency.
10. Apparatus yas claimed in claim 9 wherein said
means for applying said control signal to said saw-tooth
and a pulse samplingtdemodulator providing an output
generator comprises a monostable flip-flop triggered bythe
representative of the peak voltage of the integrator out 50 control pulses from `said comparator.
put.
6. Apparatus as claimed in claim 5 wherein said shap
ing circuit comprises a squarer to convert the input sig
VHals into a rectangular waveform, a iirst self-timing
monostable flip-flop triggered by the leading or trailing
edge of the rectangular waveform .to produce a short
duration pulse for controlling the pulse sampling demod
l1. Apparatus as claimed in claim l0 wherein said
means for applying said control signals to said multivi
vibrator comprises a circuit for applying impulses from.
said monostable flip-flop las trigger impulses to said multi
vibrator.
.
.
12. Means for transmitting information represented by
`a plurality of direct voltages of varying magnitudes com
ulator land a second self-timing monostable Hip-Hop trig
gered »by the trailing edge of the output- pulse of the ñrïst
. prising a sawtooth generator arranged, on application of
flip-flop for cutting oft and re-starting the integrator.
7. Apparatus for converting information Irepresented
60 tude of which increases from a datum Iat a predetermined
by a `direct voltage of varying magnitude into an alter
nating voltage having a frequency representative of the
:amplitude of the direct voltage comprising »a linear saw
tooth Igenerator arranged, on application of a control sig
nal, to produce a saw-tooth signal the amplitude of which
increases from a datum at a pre-determined rate, com
parator means coupled to said saw-tooth generator to
a control signal, to produce a sawtooth signal the yampli
rate, comparator means coupled to said sawtooth gen
erator to compare «a Voltage to be transmitted with the
sawtooth generator outputvoltage and to produce a con
trol -signal when the compared voltages are in :a predeter
65 mined relationship, means for applying said control sig
nal to said sawtooth generator to cut-off and re-start said
sawtooth generator when `a control signal is produced,
means for converting the sawtooth output of »the sawtooth
compare the voltage to be converted with the saw-tooth
generator into a substantially sinusoidal Waveform,
lgenerator output Voltage and to produce a control sig 70 switching means for applying in sequence to the compara
Vnal when the compared voltages are in a pre-determined
tor each of the direct voltages `representing information
relationship, means for applying said control signal to
to be transmitted, a transmission line connected -tosaid
said saw-tooth generator to cut-olf `and re-start the saw
converting means for transmitting the sequence'of alter
tooth generator when a control signal is produced, `and
nating current :outputs of said converting means, receiving
means, including a low-pass filter, responsive to said con 75 means connected to said transmission -line for re-convert
3,045,071
ing the transmitted signals to direct voltages, a plurality
of output channels, land a distributor coupling said re
ceiving means to said output channels, said distributor
being operated in synchronism with said switching means
16
sequence to provide separate outputs representative of the
various signals being transmitted.
14. I.Information transmitting means as claimed in claim
12 wherein means are provided for transmitting over said
so that the direct voltages are fed to said output channels
transmission line a distinctive signal, separable from the
in sequence to provide separate outputs representative of
the various signals being transmitted.
13. Means for transmitting infomation represented by
the distributor with the switching of said switching means.
a plurality of direct voltages of varying magnitudes com
prising a converter for converting direct voltage informa 10
tion into alternating voltages having a frequency repre
sentative of the amplitude of the direct voltage, switching
means for applying each of the direct voltages in sequence
Vto Said converter, a transmission line connected to said
converter for transmitting the sequence of alternating cur
rent outputs, a shaping circuit connected to said transmis
sion line for converting the received signals into repetitive
pulses synchronized with the frequency of the transmitted
signals, an integrator producing «a sawtooth waveform the
amplitude of which increases from a datum at a predeter
mined rate, switch means for said integrator coupled to
said shaping circuit to be controlled by the repetitive
pulses so that said integrator produces waveforms increas
ing to »a potential dependent on the frequency of the input
signals, circuit means connected to said integrator provid
ing `an output representative of the peak Voltage of the
integrator output, a plurality of output channels, and `a
distributor coupling said circuit means to said output
other signals, for synchronizing the switching operation of
References Cited in the ñle of this patent
UNITED STATES PATENTS
1,313,483
2,098,956
2,352,634
2,400,950
tive of the peak voltages are fed to said output channels in
1919
1937
1944
1946
2,407,684
Roberts ___________ _‘.__ Sept. 17, 1946
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channels, said disributor being operated in synchronism
With ysaid switching means so that said outputs representa
Heising ______________ __ Aug. 19,
Dudley _____________ .__ Nov. 16,
Hull ________________ .__ July 4,
lPurington ___________ __ May 28,
1,
16,
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