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Патент USA US2404355

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July 23, i946.
¿40,355
c. E. ATKINS
SECRET SIGNALING SYSTEMv
Filed Oct. 2. 1943
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INVENTOR
CA EL EDWARD ,4me/MS’
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ATTORNEYS
Patented July 23, 1946
¿44,355
2,404,355
SECRET SIGNALING SYSTEM
Carl Edward Atkins, Evanston, Ill., assignor to
Tung-Sol Lamp Works, Inc., Newark, N. J., a
corporation of Delaware
Application October .2, 1943, Serial No. 504,679
9 Claims. (Cl. 1~78-22)
l
My _present invention relates to secret station
to-_station signaling systems of the general type
disclosed .and Claimed _in my Ycopending applica
tion _Serial No. 443,898, ñled May 21, 1942, and
comprises _an improved and _simpliñed system of
connects to any suitable audio frequency ampli
that type particularly adapted for secret tele
sraphìc communication.
odes of tubes _20 and 2| are biased by the network
ñer and reproducer (not shown) such as a loud
speaker or the like, while a tap on resistor I9 is
connected to the control grid of a triode 20 con
nected in tandem with a ytriode 2|. The cath
I3 and the plates of this pair of tubes are con
nected in parallel to a tuned circuit 22 which is
'In my present system, _as in that of my above
connected with the power source through the
mentioned application, secrecy is obtained by
scrambling the signal introduced at one station 10 filter I5. As hereinafter described, tube 2| oper
with _the _signal introduced at the other station
and detection of the communicated signal is ob
tained by cancellation from the incoming energy
of the modulation corresponding to the signal
previously introduced at the same station,
For an understanding of the improved system
of the present invention reference may be had to
the specific and preferred embodiment of the in
vention employing frequency modulation illus
ates to add the local signal to that introduced at
the cooperating station and hence this pair o_f
tubes may be termed the “injection mixer.” The
output of the pair of tubes 20 and 2|, appearing
across the tank circuit 22 is fed through a block
ing condenser 23 to a reactance tube 24 which
controls the frequency of an oscillator 25. The
output from oscillator 25 energizes a power ampli
ner 26 and transmitting antenna 2l.
trated Yin the drawing, of Which
Fig. l is a diagrammatic circuit drawing of the
apparatus at either of two communicating sta
tions equipped with a secret signaling system em
For the introduction of the signal each station
trap 2 tuned to the frequency of the local trans
mltter, a _receiver 3 tuned to the frequency trans
mitted at the cooperating station, a limiter 4, an
amplifier 5 and a frequency detector 6 the output
includes suitable phase shifting means and pref
erably also at least one o_f the stations amplitude
control means. Before describing speciñc circuits
suitable yfor use as the network 30, which circuits
are shown in Figs. 2 and 3, the operation of the
includes an oscillator 28 operating at a low fre
quency of say 100 cycles per second, a key 29 and
a special network 30 which includes phase shift
ing means and which delivers a portion of the
bodying the invention;
signal energy through a delay network 3| to the
Fig. 2 is a diagram of the special network of
control grid of tube I4 and another portion of
Fig. l at one station; and
the signal energy to the control grid of tube 2 I.
Fig. 3 is a diagram of the special network of
Network 3| may be any known type of delay
lï‘ig, 1 at the other station.
network, as for example a resistor-condenser
shown in Fig. 1, the equipment at each sta
tion in the speciñc embodiment of the invention 30 combination or an inductor-condenser combina
tion, and network 30 may be any network which
illustrated includes a receiving antenna I, a wave
circuit of which includes a phase shifting network
comprising a capacity 1 and adjustable resistance
8 connected in series and .Capacity 9 connected in
shunt across a resistance I0.
A resistance II,
grounded at one end, is connected at its other end
system as a whole will be described,
For con
venience in understanding the operation, the yunits
at one station, say station A, will be identified by
40 the subscript a and the units at the other station,
say station B, will be identiñed by the subscript b.
At station A when key 29a is operated, a part of
the energy is supplied through network 30a to the
ably biased by a network I3 as is also the _cathode
grid of tube 2 Ia, whereupon the output from tube
of a triode I4 connected in tandem with tube I2.
The pair of tubes I2 and I4 operate, as herein 45 2| a appearing across tank 22a modulates the
to a tap on resistance II) and to the control grid
of a triode I2, The cathode of tube I2 is suit
after _more fully described, to cancel the frequency
dQVíations corresponding to the signal previously
reactance tube 24a and a frequency modulated
signal is transmitted from antenna 21a. At sta
tion B the transmitted energy is received and am
pliñed and then demodulated in detector 5b_ The
termed a “cancellation mixer.” The plates of
tubes I2 and I4 are parallel connected and the 50 phase of the signal energy is shifted by the net
work _lb-ßb-Sb and a suitable portion thereof
output from this pair of tubes, which appears
applied from resistor IIlb to the grid of tube |212.
across a tuned circuit I5, connected to a source
of power through a ñlter I6, is fed through a
An amplified signal appears across tank |5b and
is applied through blocking condenser I'Ib and
blocking ,condenser I'l to a pair of parallel con
nected resistors I8 and I9. A tap on resistor I8 55 control I9b to the grid of tube 2Gb. Appearing yin
introduced at the local station and hence may be
3
4
the output across tank circuit 22b the signal
energy serves to modulate reactance tube 24h.
lIThis frequency modulated signal after `a brief
interval is received at station A where it origi
and the master resistors 32 and 38 together with
the numerous other tapped resistors provide
of the tube |2a.`~ In the meanwhile energy re
the control grid of tube 2| will be' of‘equal ampli
means for adjusting the volume of the signalen
ergy and the proportionate distribution thereof.
nated and upon demodulation in detector `lia. has Cil Preferably the Various phase shifting networks
its phase shifted in network 1a-Bw--Sa. A por
and amplitude control means of the system are
tion thereof is then applied to the control grid
so adjusted that th'e signal energy delivered to
sulting from the operation of key 29a and de
tude and 120° out of phase with that delivered to
livered through network 30a to delay network 3|ct' v-10 the control grid of tube 20. As disclosed in my
has been delayed in the latter network and is ap
said copending application Serial No. 501,529,
plied to the control grid of tube Marsimulta
iiled September 8, 1943, phase difference of this
neously with the arrival of the returning signal
amount in the signal energies to be mixed when
to the grid of tube |2a andin phase opposition f
the amplitudes Vare equal enhance the secrecy of
thereto. Consequently there will be no corre
th'e system vasit insures that there will be no
sponding output across tank |5a, If, however,
key 29h has been depressed during this interval, Y
the phase angle of the incoming signal will rbe,Y 1
change (in amplitude in the radiated signal irre
spective of whether one or both keys 29 are de
pressed.
such as to yield an output across |5a which can
From the foregoing description it will be ap
be heard as an audio signal at station A and 20 parent that the present invention provides an
which is also applied to the grid of tube 20a for
addition across tank 22a to the continuing signal
delivered to tube 2|a from network 30a. The
operation at station B, including the cancella
tion _of the locally introduced signal by tubes |2b
eiiicient secretY ‘station-to-station signaling sys-v
tem wherein the signal originating at one station
is scrambledk with. the signal introduced at the
oth'er station whereby simultaneous introduction
of keyed intelligence at the two stations produces
and |4b and the addition of the signal by tubes
a conglomerate of characters on a more or less
2|Jb and 2| b is of course the same as above de
capricious basis, resulting in a signal unintelli
gible to an eavesdropper. While the preferred
form of the invention utilizes frequency modula
scribed for station A. .
InV the system of Fig. 1 the network 30a and
30h may be identical but I prefer, however, in
order to provide a iiexible system with a wide
range Yof adjustment of the phase shift and of
the amplification, to employ for one network
30 the circuit shown in Fig. 2, and for the other
network 30 the circuit shown in Fig. 3. As shown
in Fig. 2, one network 3|] includes a master re
sistor 32 grounded at one end and connected at
its other end to the key 29 and a pair of sub
sidiary resistors 33 and 34 connected in parallel
to van adjustable tap on resistor 32.
tion as a'means for carrying the signal energy to
and from the communicating stations, amplitude
modulation or phase' modulation can likewise be
employed.
Y'
The following is claimed:
,
v
«
'
1. A secret station-to-station signaling system
comprising in combination equipment at each
station Vincluding receiving means, detectingv
means connected toreceive energy from said re
ceiving means, a pair of electron tubes connected
A tap on 40 inV tandem, a phase-shift network between said
detecting means and the control grid of one of
resistor 33 supplies energy to the primary of a
transformer 35 the secondary of which energizes
the grid of tube I4 through a polarity reversing
switch 36 and delay network 3|.
A tap on re
sistor 34 connects through a phasing network 31
to the grid of tube! I.
e
~
said tubes, signal introducing means, means for
creating a delayed replical with' shifted phase of,
theY signal introduced by said introducing means
and for applying the same to the control grid of
Y
the other one of said pair of tubes, a second pair
Unit 30 of the other station, as shown in Fig.
3, includes a master’resistor 38, a'tap on which
of tubes connected in tandem, a tuned output
circuit `for said first pair of tubes connected to the
'control grid of one 0f said second pair of tubes,
means for impressing signal energy from said
said signal introducing means to the control 'grid
of >the other one of said second pair of tubes,
transmitting means >and means for modulating
isV connected through a phase shifting network
including a resistor 39, condenser 40 and resistor
4|, to the grid of a triode 42. Triode 42, which
is suitably biased by a network 43, ampliñes the
signal energy and changes its phase by 18o". The
output circuit of triode 42'includes the primary
of a transformer 44 the secondary of which is
connected to _parallel connected resistors 45 and
46. A’ tap on resistor 45 is connected to th'e grid
of tube |4 through delay filter 3| and a tap on
the incoming energy` atene-stationenergycorr
resistor 46 is connectedÁ to the control Vgrid of
responding tothe signal previously introduced'
tube
2|.
,
'
Y
„
'
For eiiicient operationof the above described
system the oscillators 28a and 28h should be
synchronized and their outputs maintained -in
phase. Known stabilizing means could be pro
vided at each station for this purpose o1' the fre-_
quency of one oscillator could be locked to that
of the other by the transmission from one sta
tion to the other of a modulatingV tone asV dis
closed in a copending application of mine, Serial
No. 501,529, iiled September 8, 1943.v The net 70
works '|--8-,9, 39-40-4| ,'31 and 3|, together
with the Apolarity reversing switch 36, provide
ample means for adjusting the phase of vthe
signal energy aty any point inthe system, the
amplifier 5 and triode 42 provide amplification, 75
the energy transmitted by said transmitting
means by the output from saidl second pair of
tubes- whereby said ñrst pair> of tubes may 'be
operated as aV cancellation mixer'tocancel from
into 'the system at the same station and said sec
ond pair of tubes may be used to scramble the'
outgoingv signal withrthe signal introduced at
the other station.Y
ì
Y
_
_
'
,
‘
2.."In a secret stationáto-station signaling sys
tem of the type wherein signal energygintroduced
at onestat'ion and transmitted Vtherefrom to the
other station >isfrriiired at the -latter’station with
signal energy introducedatthe latter station, the
improvement which „comprises atv eachstation a
pair of electron~ tubes Vconnected in tandem, means`
for impressing upon thegrid of one of said ,tubesY
demodulated energy received from the other sta
tion,;means f_orirn'pressing upon theY grid ofïthe.v
other of `,said tubes a delayed- replica ofthe signal
energy introduced at the same station for cancel
2,404,355
5
6
ing in the output oi said tubes that portion of
the demodulated energy received from the other
mixer comprising a second pair of electron tubes
connected in tandem, means for energizing the
station but previously originating at the same
station, a second pair of electron tubes connected
in tandem, means for energizing the grid of one
control grid of one of said last mentioned pair
of tubes with the output of the cancellation mixer
and means for energizing the control grid of the
of said second pair of tubes from the output of
said ñrst pair of tubes, means for energizing the
grid of the other of said second pair of tubes With
signal energy introduced at the same station, and
means connected to the output circuit of said
last pair of tubes for modulating the energy
transmitted from the station.
3. The method of operating a secret station-to
other one of said last mentioned pair of tubes
with signal energy introduced at the same station.
6. In a secret signaling system of the type de
scribed, the combination at each station of a low
station communication system which comprises
at each station dividing the signal energy into
two portions, delaying one portion and shifting
the phase thereof, scrambling the other portion
frequency source of signal energy, a key, a net
work receiving energy from said source under
control of said key, said network including phase
shifting means and means for dividing the energy
received from the source into two portions, means
for scrambling one of said portions with energy
received from the other station and corresponding
to av portion of the energy of the source at the
other station, transmitting means, means for
with signal energy introduced at the other sta
modulating the energy transmitted by said trans
tion, utilizing the scrambled portion to frequency
modulate the energy transmitted from the station, 20 mitting means with said scrambled Portions,
means for delaying said other portion, receiving
and utilizing the delayed phase shifted portion
and detecting means, and means for utilizing said
for separating the signal energy introduced at
delayed portion for unscrambling the detected
the other station from the energy received and
energy received from the other station.
detected at the same station.
7. The combination according to claim 6
4. The method of operating a secret station 25
to-station communication system which comprises
wherein said network at one station includes a
at each station dividing the signal energy into
two portions, delaying one portion and shifting
resistor, grounded at one end and connected to
said key at its other end, a pair of resistors con
nected in parallel to a tap on said ñrst mentioned
resistor and a pair of phase shifting circuits each
the phase thereof, scrambling the other portion
with signal energy introduced at the other station,
utilizing the scrambled portion to modulate the
energy transmitted from the station, utilizing the
delayed phase shifted portion for separating the
signal energy introduced at the other station from
the energy received and detected at the same sta
connected to a tap on one of said last mentioned
resistors, whereby one portion of the signal energy
is delivered through one of said phase shifting
circuits and the other portion through the other
35 of said phase shifting circuits.
8. The combination according to claim 6 where
in the network at one of said stations comprises
a resistor grounded at one end and connected
justing the relative phase of the signal energies
to said key at its other end, a phase shifting cir
to be 120° out of phase when scrambled.
5. In a secret station-to-station signaling sys 40 cuit connected to a tap on said resistor, a triode
tion, maintaining the signal energies introduced
at the two stations equal in amplitude and ad
tem of the type described, the improvement which
comprises at each station a cancellation mixer
energized from said phase shifting circuit, and a
pair of parallel connected resistors in the output
of said triode whereby said portions of signal
and an injection> mixer, said cancellation mixer
energy may be tapped from said last mentioned
including a pair of electron tubes connected in
tandem, means for applying to the control grid 45 resistors.
9. The combination according to claim 6 Where
of one of said tubes energy having components
in the phase shifting means of said network at
corresponding to the signal previously introduced
one station are arranged to shift the phase of
at the same station and the signal introduced at
one of the portions of energy relative to that of
the other station, means for applying to the con
trol grid of the other tube energy corresponding 50 the other portion of energy and the phase shifting
means of the network of the other station are
to the signal previously introduced at the same
arranged to shift the phase of the signal energy
station but 180° out of phase with the correspond
prior to division into portions.
ing component of energy applied to the control
CARL EDWARD ATKINS.
grid of the ñrst mentioned tube and said injection
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