Improvements relating to Telegraphic Transmission.
Year: 1894

page_text: Date of Application, 11th June, 1894-Accepted, 11th July, 1895
Improvements relating to Telegraphic Transmission.
A communication from abroad by MICHAEL IDVORSKY PUPIN, of 46 West
72nd Street, New York, United States of America.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
The object of the invention is to enable a large number of messages to be sent
simultaneously over a single conductor by means of currents of the same or of
different periodicities. Periodic currents will act, with reference to one another on
a conductor, like sound-waves in air, each being transmitted independently of the
rest, and each current selecting at the receiving end of the line its own translating
are different currents
device out of as many translating devices as there
transmitted.
If for example a person at one station wishes to communicate with another
person whose station corresponds to a periodicity of 150, then the transmitting
station must be set either permanently or at least temporarily at such periodicity.
Where it is intended that the stations should only be used in pairs, then each pair
is permanently set at a predetermined periodicity and any number of such pairs
may use a common trunk or main line, but if on the other hand it is intended that
any one station should be able to call up any of the other stations then means for
varying the periodicity must be provided at each transmitting station.
In the accompanying drawings,
Fig. 1, is an electrical diagram illustrating the principle of the invention.
Fig. 2, is a diagram showing symbolically the devices employed, the branch
circuits being in parallel.
Fig. 3 is also a diagram showing the branch circuits operated inductively by the
line in series with the primaries of the transformers whereof the said branch
circuits are secondaries.
Similar numbers of reference indicate like parts.
Referring first to Fig. 1, UW is the main line, to which is connected in
parallel any number of branch conductors, I, II, III, &c. Each branch contains
self-induction coils, a', 6', &c., in series with condensers, a³, 63, &c. The coils and
condensers are used for electrical tuning, as hereafter explained.
The main line is grounded just beyond the point W and the continuation of the
main line in the opposite directions beyond the point marked U leads to the trans-
mitting stations where alternating currents of different frequencies are impressed
upon the main line. Say an alternating current of 130 periods per second is sent
over the line. Then any one of the branches as IV can be made resonant to this
This branch is theu selective
current by adjusting its electro-magnetic constants.
with regard to this frequency. Similarly every other branch can be made selective
to some other frequency to be impressed upon the line at the transmitter end.
In such a system each branch will have an appreciable current in it only when
there is a current on the main line of a frequency equal to that to which the
particular branch is resonant.
Referring to Fig. 2, 1 is the main line connected with three telephone trans-
mitters, 2, 3 and 4, in parallel with battery 5. The secondary coils, x, y, z, of the

page_text: transmitters, are connected in parallel to main line at 9 and to ground G, G1, G2.
In front of each transmitter is a tuning fork, as 6, 7 and 8. Let the fork 6 be
tuned, to. illustrate, to the note A, the fork 7 to B and the fork 8 to C-hence
three periodic electromotive forces, each of a different periodicity, will be impressed
upon the main line 1 at the point 9 simultaneously. At the receiving end of the
line, starting from point 10, may be any number, say three, branch circuits, a, b, c,
consisting essentially of coils L, M, N for furnishing the auxiliary self-induction,
and condensers O, P, Q for furnishing the auxiliary capacity by the proportioning
of which self-induction and capacity, the circuits are tuned. All of these circuits
are connected to the ground G³. The auxiliary parts of these three circuits are
the telephone receivers R, R' and R2, which are placed in inductive relation with
coils L, M, N and the small coils surrounding permanent magnets or soft iron
cores l, m, n and also three keys, 19, 20, 21.
Say it is required to send a message from transmitter 4 to branch a (what follows
is also true of any other branch as b or c). The coil L has a fixed self-induction,
and the condenser has a fixed capacity, with which the self-induction and
capacity of the line and the variable self-induction and capacity of the transmitting
branch 4 will respond to a frequency C. Hence the operator at 4 will use a fork
of frequency C, and then adjust auxiliary coil z until the electrical periodicity of
circuit Z, Z, 9, 1, 10, L, O, a G'is C. The operator at 4 can tell when this frequency
is reached by the loudness of the sound in the telephone. The telephone is acted
upon inductively by coil Z or any other convenient part of the circuit at the
transmitting end, and serves as a control for the operator. The sound of the
telephone R calls the attention of the operator in the branch circuit a. This
telephone is operated similarly to T. He answers the call by means of breaking
the circuit several times in quick succession with the key 19, and the operator
hears this signal in telephone T. He then closes the battery circuit which works
the receiving transmitter r, and the receiving instrument 24 is then ready to
receive the electrical impulses from the line. These impulses are given in the
following way - -Whenever the operator at 4 closes key 17, an alternating current
of frequency C passes to the branch a, and, by its action upon the magnet 1,
sets the diaphragm of the receiving transmitter in vibration, thus producing, a
strong induced current of the same frequency in the secondary coil of the trans-
former, 23, of this transmitter, which current, passing through the coil of the
sounder 24 repeats the signals sent by the key 17.
This communication of signals will in no way be interfered with by the
simultaneous transmission of signals between the circuits and c and the trans
mitters 2 and 3 as long as these transmissions employ a frequency different from
the frequency employed in the branch a.
It should also be observed that each receiving instrument, as 24, may have an
adjustable condenser in series with it, in order to reduce its electromagnetic
impedance to a minimum for the frequency of the branch..
Any number of branches both at the receiving and at the transmitting end, may
be employed each branch operating simultaneously as receiver and as transmitter,
provided that it has both the receiving and the transmitting apparatus. In Fig. 2
the receiving apparatus only, in the branches abc is shown. Thus in branch at
the receiving end is a key, 20, coil M, condenser P and iron core or permanent
magnet m.
The core
m operates the transmitter diaphragm at and local
circuit 25, and through the transformer 26 the sounder 27. Similarly in branch ic
is a key, 21, coil N, condenser Q and iron core n. The coren operates the
transmitter diaphragm at and local circuit 28, and through the transformer 29,
the sounder 30. In each branch, like a, there may be any number of sets of
receiving and transmitting, apparatus all connected in multiple with this branch...
Referring now to Fig. 3, here the main line 1, instead of connecting directly
with the local circuits a, b, c, is placed in inductive relation with them by means
of transformers, the primaries 31, 32, 33 are in series in the main line, while the
secondaries 33*, 34, 35 are included in the local circuits. It will be noted,

page_text: therefore, that in Fig. 1 the branch circuits a, b, c are in parallel with the main
line, while in Fig. 3, the primaries inducing the brauch circuits a, b, c are in series
with the main line.
No synchronically moving mechanism is used at opposite ends of the line, and
no apparatus is needed which might interfere with the selection effected at the
receiving end for any reason. The various circuits of the system are placed in
electrical resonance with the several periodic currents of previously selected
periodicity by properly proportioning the electromagnetic constants of said circuits.
The self-induction and capacity of the auxiliary coils and condensers respectively
in the receiving branches of the various circuits retain a fixed value and the tuning
is performed in the transmitting branches by properly proportioning the self-
induction or the capacity, or both, of the auxiliary coils and condensers in these
branches.
In place of telephone transmitters I may use oscillators or vibrators, or any
other contrivances adapted to produce and transmit to line, currents of different
predetermined periodicities. Both at the transmitting and receiving ends the
telegraph keys and sounders, here introduced merely for the sake of their
simplicity, may be replaced by any suitable telegraphic, transmitting and receiving
apparatus.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me
by my foreign correspondent, I declare that what I claim is
1. A telegraphic system comprising the combination of a line conductor, a
branch line, in either direct or inductive relation to the main line a means of
imposing on said conductor from said branch line a periodic electromotive force,
a telegraphic transmitting instrument in said transmitting branch and, at a distant
station, a receiving branch line in either direct or inductive electrical communication
with said line conductor and operating a telegraphic receiving instrument; the
receiving branch being placed in electrical resonance with said electromotive force
by properly adjusting the electromagnetic constants of the line conductor and of
the receiving branch.
2. A telegraphic system comprising two or more circuits, with a line conductor
common to all of them, each receiving circuit being electrically tuned to a
previously selected periodicity by properly proportioning its electromagnetic
constants, a means of imposing upon each circuit a periodic electromotive force
which will be in electrical resonance with the circuit and in each circuit a telegraphic
receiving and transmitting apparatus.
1141 1
T
1004
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.