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Патент USA US2406353

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Àm@ 2?@ 194@
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Filed July l?, 1943
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Filed July l?, 19425
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Filed July 17, 1945
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Filed July 17, 1943
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Patented Aug. 27, 1946
Qscar Myers, Mount Vernon, N. Y., assignor to
Bell Telephone Laboratories, Incorporated, New
`iZork, N. Y., a corporation of New York
' Application July 17, 1943, Serial No. 495,126
11 claims.
(Cl. 179-15)
The present invention relates to the trans
mission of speech or other types of signals with
privacy. The invention is based upon the use
of variable time delay in transmission of signal
elements to render reception of the message
A known type of privacy uses a moving mag
the record tape and these are designated A, B, C,
D, E, F, G, H and I. If magnet A is used, since
it is situated nearest to the recording magnet, a
delay of one unit is introduced. Magnet B in
troduces two units delay, etc. The above code,
together with its decoding sequence, could be
expressed in terms-of the electromagnets that
netic tape with cooperating electromagnets
spaced along the tape at equal intervals as a
means of producing unequal time delay in the
transmitting code then being A B C G F I-I C F D
G E and the decode sequence being C B D GI D
transmission of signal elements. A commutator
or equivalent is used to switch electromagnets,
serving as individual recorders or pick-ups, into
are used in successive commutator times, the
` C G F E.
The connections between the com
mutator segments and electromagnets at the
transmitter would have to be different from those»
at the receiver if this code were.. used. This
circuit with the line in definitely timed short
intervals, A similar arrangement is used at the l5 would be satisfactory in the case of one-way
receiver to decode the message. In such a sys
tem the sum of the delay introduced at the trans
mitter plus that introduced at the receiver is the
same for all signal elements. For illustration,
assuming a commutator of ten segments individ
ually wired to the electromagnets, the total delay
transmission or two-way transmission on a four
wire basis using four machines. Two-way trans
mission with two machines each serving alter
nately to receive and transmit would also be
possible with diiierent codes usedl for opposite
directions provided the necessaryV switch-overs
were made at both stations whenever the direc
at both transmitter and receiver is ten units (a
tion of transmission is reversed. In order to
being in this case one tenth the rotational
avoid the rather complicated switching that
period of the commutator) so that if a delay of
three units is introduced in transmitting a given 25 would be involved it has been proposed to use
self-converse codes, meaning that if one ma
signal element, a delay of seven units must be
chine is set to code a message for transmission
introduced for that element in the receiving and
with a self-converse code, it can without switch
decoding process. With a given wiring between
over decode a received message sent with the
commutator segments and electromagnets‘ the
the code is repeated in each rotation of the com 30 same code.` This imposes the limitation that the
delays introduced into the individual` signal ele
mutator, “code” here being used to indicate the
ments as transmitted must be the same as the
scheme of time delays introduced in the ten in
delays introduced into the elements as received,
dividual signal elements sent in commutator
and that as before the sum of the delays intro
times l to lû, inclusive. This can conveniently
be expressed as a series of ten numbers, for ex 35 duced into the same signal element at both trans
mitter and receiver must be equalto that for each
ample, i 3 7 5 8 3 5 Li 7 5 to indicate the delays
of the other elements. One such code, for illus
of the respective elements. In View of the fact
tration, might be B G E G C F C E H D.
that each-element must experience a total delay
Applicant has found that for every self-con
oi ten units at transmitter and receiver together,
verse code a pair of electromagnets must be used,
if the message is to be successfully decoded, the
one giving a delay complementary to theY other,
time delays introduced at the receiver in order
and that `the commutator segments to which
to decode the message sent by this code would
these pairs are connectable also fall into pairs.
have to be 9 '7 3 ¿i 2 '7 4 6 3 5 for the respective
In the case of a ten-element code, the electro
signal elements considered above, but since these
elements are variably delayed they are actually 45 magnets andcommutator segments can be ar
ranged in a table comprising forty-live possible
received in a diñerent order from that which they
pairs of electromagnets and commutator seg
originally had, the received order being 3 5 4 2 1
ments. This fact enables a straightforward type
7 9 6 8 i0 on the basis of an original order of 1,
of selection to be made for setting up all possible
2, 3, etc. Ifv the receiver delays given above are
identiñed‘with the individual signalelements the 50 self-converse codes and gives the general pattern
of a switching circuit for selecting the codes.
receiver code expressed in terms of delay to be
An object of the invention is to facilitate se
introduced into the signal elements as received
lection of diiîerent codes for both transmitting
and receiving and especially to provide for quickly
In the known type of privacy system referred
to there are nine electromagnets spaced alongV 55 and automatically changing codes.
The nature of the invention and its Various
objects and features will be better understood
from the following detailed description in conu
nection with the accompanying drawings in
which Fig. 1 is a table from which to determine
interconnections between reproducer magnets
and commutator segments in making upk Selin
converse codes;
Fig. 2 is a partial View in perspective of one
relatively simple matter to arrange switching
mechanism to select the codes one after another
in any desired sequence.
One such switch mechanism is shown in Fig.
2 and comprises a rotating cylinder 2Q with inn
sets, two of which are shown at 2l and 22, ex~
tending the length of the cylinder and situated
close together entirely around the cylinder. Each
inset has five raised portions, which when di
type of code selector according to the inven
tion; and
Figs. 3, 4, 5 and 6 when placed together in the
manner shown in Fig. '7 show in schematic dia~
spring to be closed, as indicated, for example, at
25 and 26. There would be forty-five such springs
gram form the circuit of a complete two-way
23 any ñve of which are operated at a time as
rectly underneath corresponding springs 23, raise
the springs and cause two pairs of contacts per
privacy system in accordance with the invention. 15 determined by the positions of the lugs on any
In Fig. 3, the magnetic tape is shown at II
one insetrfrîl or 22, etc. One 'setpf contacts, 25,
passing "overwpulleys I2 forY driving itY and the
would connect a particular reproducer pick-up
electromagnets are shown below the tape, there
coil with a particular commutator segment I, 2,
being nine reproducer magnets lettered A,
3,'etc., of the regular set. The other set of
B . . .. I, a recording magnetV I3 and an eraser
contacts, 25, would connect a particular pick-up
magnet I4. Each of the reproducer magnets` is
coil with a particular commutator segment I',
adapted, by switching devices to be described, to
2', 3', etc., of the interlace set.
`be connected to an individual segment of the
The insets 2l, 22, etc., can be made of metal,
commutator shown in developed form at the
plastic, ñber or other suitable material and they
right of Fig. 3 with the segments in a vertical
can be inserted in slots in the cylinder and can
line. These segments are numbered I to II) and
be readily interchanged among themselves by
I' to _'I0’, the latter being interlaced with the
.simplyl withdrawing them and reinserting them in
former. In the drawings, these segments are
diiïerent order.
shown widely separated but in practice it will be
The cylinder 2i! can be stepped to bring the
understood that they would be situated as closely
next inset underneath the row of forty-five
together as feasible in accordance with usual
switch springs 23 by means of a pavvl and ratchet _
commutator design. It will be understood that
in practice the tape II may be mounted on the
rim of a disc and that the commutator may be
actuated at `timed intervals by a clock-operated
operated by stepping magnet 3G which can be
contact or from the commutator drive, as for
circular and mounted so that the same shaft 35 instance, after each rotation of the commutator
rotates the tape disc and the commutator brush
or after a given number of commutator rota
I5 over the segments.
Reference will now be made to Fig. l which
It will be understood that the insets are cut
consists of forty-five boxes in each of which
s0 as to select five pairs of magnets, and accom-v
appears a pair of letters designating reproducer 40 panying commutator segments from those given
magnets and an associated pair of numbers des
in the table of Fig. l to provide self-converse
ignating commutator segments. vThus, in the
codes as previously explained, each strip with its
single’boX appearing at the top of the figure, the
lugs representing one code. The interlace code
notation indicates that if reproducer A is con
can be entirely independent of the regular code.
nected to commutator segment 2 and if repro 45
Reference will now be made to Figs. 3, 4, 5 and
ducer I is connected to segment I , two of the
6 arranged as shown in key Fig, '7. It will be
signal elements of a ten-unit section of signal
noted that forty-five relays are shown in Figs.
will be coded in a self-converse code. The two
5 and 6 arranged in the same manner as the
signal elements sent by such arrangement will be
boxes in Fig. l, except that for co-nvenience of
correctly decoded at the receiver with identical 50 arrangement on the sheet the table is turned on
connection of reproducersA and I to the commu
its Vside in Figs. 5 and 6 with the relay corre-=
tator segments 2 and I thereat, assuming, of
spending to the uppermost box in Fig. 1 shown
course, synchronous operation of the machines.
, at the extreme right in Fig. 6. The bottom row ’
A complete ten-element self-converse code can
of boxes of Fig. 1, therefore, corresponds to the
be built up by choosing any rive boxes that re
vertical column of relays at the left side of Fig. 5.
Each relay has two armatures and it will be ob
sult in a connection to each of the ten commu
tator segments with only one connection to each
served that the armatures are permanently oon
segment. There may and usually will be more
nected to commutator segments and when at
tracted close contacts leading to the pick-ups.
than one connection to the same reproducer.
It will be noted that in any self-converse code, 60 Taking the left-hand column of relays of Fig_ 5,
such as that given earlier in this description by
for example, and reading from the tcp down, the
left armatures are connected to respective com
' way of illustration, the letters representing _the
mutator segments I, 2, 3, e, 5, 6, 1, 8 and 9 while
amount of delay given to a signal element appear
the right-hand armatures are all connected to
in pairs such that the sum of the delays is the
same for all pairs. Moreover, the letters corre 65 segment I0, A corresponding rule with one less
total number is followed in each of the other
spond in their position in the code to com
columns of relays. Again `considering the left
mutator segments and, in the case of each pair,
column, the left armatures can be closed
are separated by a number of segments equal to
to Vconnect individually to reproducers A, B, C,
the number of delay units represented by oneV of
etc., reading from the top relay down, while the
the pairs, counting around the commutator re 70 right-hand armatures have an opposite order of
garded as a closed ring.
connection, that is, they can be closed to con
Since these fort’y-iîve sets of connections rep
nect individually to reproducers I, H, G, F, E, D,
resent all of the possible self~converse codes when
C, B and A. A similar scheme is followed in the
taken five at a time as explained,` it becomes a 75 GEES@ Oi the other columns except displaced one
reproduc'erY element since the number of relays
decreases’byA one per co-lumn.
It‘ willlbeî seeni by tracing' out the wiring that
whenever a particular relay is energized it con
nects- Vie pair of picl§~ups to the pair of com
mutator segments that are given in the corre
sponding box. in Fig. 1. Taking relay G0 (Fig. 5),
for example, which corresponds to the box
marked 40 in Fig. 1, this relay when energized
closes’` both its armature contacts, the left arma
ture connecting commutator segment 4 to repro
ducer‘D and the right armature connecting com
For simplicity of drawing. onlyf‘a few connec
tionssareshowniinlFig;14ibetween the energizing
lea-ds: fori theirei'aysrinfFigs'. 51and16 and the selec
to'rflíanksi. It.wil1 be'. obvious, however; how all
of the' connections-î indicated inthe diagram of
Figi: 1f can; be‘i‘provided'. for by ` merely connecting
the individual.- leads’A from the code relays to
A great
10 proper' ch’c's'enipointsî ofi the selectors.
variety oficonne'ction'sïis' possible since the codes
can’ be. seti uprsin~` any' desired sequence and the
mutatorse‘gm‘ent Iâ'to reproducer F. It is merely
same code can-bef-used over and over again in
necessary, therefore, to energize five relays to pro
vide av self-‘converse code, these relays corre
spondin‘g»` to any suitable five boxes in the dia
different sequences.'`
'Iîh’e‘sele'ctin'g circuit-‘of Fig. 4’ and the relays on
Figs. 5 and ôrdetermine thecoding to be used for
Each relay in Figs. 5 and 6 has an individual
energizing- conductor extending off the top of
Fig. 5 to the selecting circuit in Fig. 4 where a
ground can be applied to any of these leads, the
opposite’ side of each relay being permanently
the'normalcommutator'segments I, 2, 3 Y. . .,I0.
A duplicate-set of’equipment is indicated in the
upper part of Fig, 3 to determine the coding to be
used' for’ the interlace set. of segments I', 2',
|0'~, this equipment' consisting of a tim
ing and selector circuit IZI, which may be en
tirely‘si'milar to that shown on Fig. 4, and forty
ñve selecting relays (interlace set) |22 which may
Referring to Fig. 4, two banks of selector
switches are shown, those at the left being num 25 be similar to those shown in Figs. 5 and 6. 'I‘he
wiring betweenfthe relays and selectors and the
bered I0!)k to E05 and those at the right being
wiring within the timing’and selector circuit in
numbered |00 to III. The switches |00 to |05
the case-of thi’s'interlace equipment IEI, |22 may
are `Steppe@ by stepping magnet I I2 and switches
be‘different from’ that used in the normal set of
|00? to III are stepped by magnet H3. 'I'hese
switches are stepped under control of clock-op 30 equipment of Figs. 4, 5 and 6; since the normal
and interlace codes can be entirely independent
eratedV contacts H4 which when closed energize
ofeachotlier. Also the Wiring between the re
either stepping magnet H2 or H3 depending
lays'andcommutator segments may be different
upon whether or not the transfer relay H5 is
in the’two- cases.
energized or deenergized. This relay is, in turn,
In the use of this equipment to transmit and
controlled by the two selector switches |05 and
receive, the telephone or other signal generating
III‘I in tandem from ground H6 through contact
means |3I and the telephone or other signal re
of selector |00 through conductor leading through
ceiving means |32 are arranged as in Fig. 3 to be
the code‘plug H1. Contact of selector |06 and
connected into the system by the two-position`
winding of relay I I 5 to battery. It is to be under
three-spring switch |30, which is shown in nor
stood that a number of conductors extend bc
mal'or receiving position. The “line” |33 may
tween the sector of selector i 00 and that of selec
bethe audio input to a radio or other signal
tor |05 and that the code plug provides cross
connected‘to battery as shown in Figs. 5 and 6.
connections between these conductors as may be
desired to introduce a variable operation into
transmitter and theY audio output of a radio or
other receiver, or it may be one side of an or
relay M5L For example. with the relay H5 in 45 dinary telephone- or other signal line the oppo
site side of which in any case is assumed to con
the‘condition shown the next time contacts H4
sist, in' this figure, of grounded terminal of re
are closed stepping magnet I i3 is energized caus
corder coil I3 but may, if desired, be metallic.
ing switches |00 to III to take an additional
With switch |30 in the position shown, coded
step. If after such step
taken switches |00
and |05 find a closed circuit to ground, relay H5 50 speech' or other signall received over line |33 is
sent tlt'irougl'i'centralswitchV spring‘of switch |30 .
is energized but if no circuit to ground is closed
and,` conductor I 35 tothe recorder coil I3 and
in this position of switches |00 and |06, relay
makes 'a record of coded speech or signal on the
H5 remains- unenergized. The wiring between
tape H. As different parts of the coded mate
switches if??? and |05, together with that inside
the code plug, may be such as to cause relay H5 ¿a Si rial is picked up by the coils A, B, C, etc_ the
brush I5 is passing over the commutator seg
to be operated or unoperated for varying lengths
ments and momentarily connecting these indi
of time.
vidual coils inproper order to the receiver |32,
Another transfer relay B20 is also operated in
through the upper spring of switch |30, to decode
parallel with transfer relay I l5. The purpose of
relay IZiD' is to furnish grounds to the movable 60 the. messagethe order of connection being de
termined by the yrelays in the regular and inter
arms of either the selector switches |00 to |05
lace sets of selecting relaysV as previously de
or |01 to III. With relay |20 unoperated as
shown grounds are supplied to the wipers of se
In transmitting, the talker or user pushes
lectors |01 to HI. With the wipers in the posi
switch |30 to its upper position so that the trans
tions shown these grounds cause energization of
mitter I3Il is connected to recorder coil I3 and
the following relays on Figs. 5 and 6: I, I3, 26,
the message is recorded on the tape I I in normal
35 and 40. These relays, in turn, set up the fol
form, the coding taking place by the relays con
lowing code using the notation given in Fig. l:
A-2 I-l., C-G G-3, C__S Cif-5, B-9 H-7, F-lO D-4.
If with the switches in the position shown the
relay |20 were energized supplying grounds to
the selectors 0n the left, the following relays in
Figs. 5 and 6 would have been operated: 8, I9,
necting Various ones of the pick-up coils A, B, C,
etc. individually to the commutator segments and
thence via brush I5 and middle switch spring of
switch |30 -to the line |33.
It is to be understood that various substitu
24, 29 and 42 and the following code would have 75 tions, alterations and modifications may be made
within the spirit and scopeof the claims, which
What is claimed is:
1. In a speech privacy system in which differ
ent speech fragments are delayed in transmission
-by different amounts of time, a plurality of in
dividually actuable devices each determining a
diiferent transmission delay time, a circuit and
circuit contact for. actuating each device, said
contacts being arranged in pairs, the devices con
trolled by the contacts constituting any one pair
determining respective transmission delays the
sum of which is a constant, and means selectively
operating said pairs of contacts.
2. In a privacy system in which a succession of
delay elements is used to >introduce successive
equal units of delay into signals together with
means for allotting time periods to said elements
for individual operation, means to code or decode
the signal comprising switches associated to be
always operated in deñnite pairs, each pair of
7. In a privacy system including a moving rec-
ord medium for signals vand reproducers spaced
along said medium, and timing means for divid
ing the signals on a time basis, means to provide
a plurality of paths between said reproducers
and said timing means, switching means for clos
ing said paths in predetermined pairs to produce
time shifts in a pair of signal fragments such
that the time shift in one fragment is the-.con
verse of that in the other, and means to select
groups of said switching means.
8. In a signal privacy system using a moving
magnetic tape, electromagnets spaced therealong
and a commutator having segments, for arrang-~
ing signal elements in different time sequences in
cycles, switches associated in inseparable pairs,
one switch of a pair when operated closing a cir
cuit from one of said electromagnets to one oi
said segments and the other switch of the pair
20 when operated closing a circuit from one of said
electromagnets to a different oneV of said seg
switches when operated determining a particular
ments such that the time sequence, within a cy
pair 0f delay elements to be used and particular
cle, given to a signal element by closure of one
time periods allotted to them for operation such
of said circuits is the converse of that given by
that the sum of the -delays introduced into sig
closure of the other circuit, and means for selec
nals by the two elements of the pair is a constant
tively operating said pairs of switches in groups
for all pairs and the time periods allotted tothe
elements of a pair for operation are always sep
9. The invention claimed in claim 8 in which
arated in time by a number of time periods cor
said switches comprise electromagnetic relays, a
responding to the number of units of delay intro» 30 selector circuit having successive positions,
duced by one of the elements of the pair.
l means in each position of said selector circuit-for
3. The invention claimed in claim 2 in which
operating a group of said relays, and means to
said switches comprise pairs of double contact
move said selector circuit from one position to
Y switch springs and cams for operating said pairs
individually and selectively.
l0. The invention claimed in claim 8 in which
4. The invention claimed in claim 2 in which
said switches comprise pile-ups of pairs of
said switches comprise sets of switch spring pile
ups, each pile-up compri-sing two switch ele.
ments, and means for actuating said switches
_ springs and said meansforselectively operating»
said pairs of switches comprises a rotatable cyl
inder containing projecting lugs on its surface for
comprising a rotating drum and -code strips re 40. lifting selected groups of spring pile-ups when
movably mounted on said drum, each code strip
said lugs pass underneath »said pile-ups.
having raised lugs for passing under and lifting11. In a signal privacy system having a' travel
a selected spring pile-upV to close the pair of
ingrecord medium and N reproducers spaced
switch elements thereof.
along said medium and including a distributor
5. The invention claimed in claim 2 in which 45 ofV P segments for dividing the signal into frag
said-switches comprise relays each when operat
ments in time, paths extending between each
ed closing two circuits for selecting the'two ele-l
reproducer and each segment, said paths being
ments of a pair, and means for selectively oper
NP in number,
ating said relays.
Y6. In a privacy system in which message cur 50
l rents are divided on a time basis into short frag
ments and the fragments are transposed in time
switches each controlling closure of a definite
in irregular manner in recurrent cycles and in
pair of said paths such that one signal fragment
which the number of fragments in each cycle is
is coded in converse relation to the other, and
even number, the method of building up self 55 means to select and operate said switches in
converse codes comprising conditioning in ad
groups of
vance the fragment transposing means to trans
pose the signal fragments in pairs such that the
time shift in one of the two fragments of the pair
is the converse of that in the other and selecting
a self-converse code.
and operating enough of said transposing means 60
to provide the proper number of pairs of frag
ments to fill up one cycle'.
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