Improvements in Multiple Telephony.
Year: 1892

page_text: Date of Application, 27th Dec., 1892
Complete Specification Left, 1st Sept., 1893-Accepted, 28th Oct., 1893
PROVISIONAL SPECIFICATION.
Improvements in Multiple Telephony.
We, MAURICE HUTIN, of 46 Rue Caumartin Paris, France, and MAURICE
LEBLANC, of 63 Allée du Jardin Anglais au Raincy (Seine et Oise) France,
Engineers, do hereby declare the nature of this invention to be as follows:-
manner.
This invention relates to means of making a single line available for simultaneous
transmission of different telephonic communications over great distances. For this
purpose, alternating currents of different frequencies are employed in the following
An alternating current of high frequency produced at a central station
by an interrupter of a continuous current or by passage of the current through
vacuum tubes is sent by a transformer into the line which has branches to a number
of transmitters and to a corresponding number of receivers. The branch from the
line to each transmitter passes to earth through the primary coil of a transformer
the secondary coil of which is in circuit with a microphone, in which circuit is
interposed a condenser of certain suitable capacity. Each receiver branch from
the line passes through a receiver and thence through a self induction coil to
earth. By suitably proportioning the capacities of the different condensers each
transmitter and its corresponding receiver are rendered capable of responding to
currents of a certain frequency and to no others, and thus each transmitter acts
with its receiver independently of all the others, and as if these two instruments
had the line to themselves.
It is preferred to employ a special telephonic transmitter combined with a call,
in each of which a coil closed on itself is acted on by another coil having currents
passing through it, in the manner of transformer coils. A receiver of like kind is
also preferably employed, instead of the ordinary magnetic receiver.
Dated this 27th day of December 1892.
ABEL & IMKAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in Multiple Telephony.
We, MAURICE HUTIN, of 46 Rue Caumartin, Paris, France, and MAURICE.
LEBLANC, of 63 Allée du Jardin Anglais au Raincy (Seine et Oise) France, >
Engineers, 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 :-
This invention relates to means of making a single line available for simultaneous
transmission of different telephonic or telegraphic communications over great
distances. For this purpose, alternating currents of different frequencies are
employed in the following manner. An alternating current of high frequency
produced at a central station by an interrupter of a continuous current or by
passage of the current through vacuum tubes is sent by a transformer into the line
which has branches to a number of transmitters and to a corresponding number of
receivers. The branch from the line to each transmitter passes to earth through
the primary coil of a transformer the secondary coil of which is in circuit with a
microphone, in which circuit is interposed a condenser of certain suitable capacity.
Each receiver branch from the line passes through a receiver of electro-dynamo
meter kind and thence through a self induction coil to earth. By suitably propor-
tioning the capacities of the different condensers each transmitter and its

page_text: corresponding receiver is rendered capable of responding to currents of a certain
frequency and to no others, and thus each transmitter acts with its receiver
independently of all the others, and as if these two instruments had the line to
themselves.
It is preferred to employ a special telephonic transmitter combined with a call,
in each of which a coil closed on itself is acted on by another coil having currents
passing through it, in the manner of transformer coils. A receiver of like kind is
also preferably employed, instead of the ordinary magnetic receiver.
The alternating currents employed should be such as are not perceptible in the
telephone receiver otherwise they would interfere with the reproduction of speech.
Experience has shewn that sounds consisting of vibrations exceeding in number
about 10,000 are not perceptible, consequently alternations of current of that
frequency will not affect the telephone. Such alternations may be readily obtained
by introducing a high speed interrupter in the circuit of an accumulator battery,
the interrupter being a wheel with alternate conducting and insulating segments on
its rim, which may be driven by a small electromotor. Although this would not
give currents of sinusoidal form, they would be rendered approximately so by the self
induction of the circuit. When it is necessary to have alternating currents of
considerable energy, the following arrangement should be adopted. First,
alternating currents of desired frequency but of moderate energy should be pro-
duced as above described, or by the oscillatory discharge of a condenser in a self
induction circuit, or by passing battery currents through vacuum tubes, for it has
been ascertained that when a vacuum tube shews streaks the current passing
through it is discontinuous, and if the primary circuit of a transformer be included
in the circuit of the tube, the secondary circuit of the transformer is traversed by
an alternating current of great frequency.
The electricity started by any of the above means being communicated to a
machine of Gramme kind made without iron, becomes thus reinforced to high
energy..
Thus alternating currents of frequency 10,000 and upwards, even to 100,000,
may be obtained. With such currents no magnetic receiver could act, consequently
recourse must be had to a receiver in which one current acts on another as in an
electro dynamometer, as shewn in front view and section by Fig. 2, where there are
two parallel coils connected in series, the one carrying an insulating diaphragm
which will vibrate in response to currents of high intensity. The call may be made
by causing strong vibrations of the speaking disc by inserting as shewn in Fig. 3 a
trembler in shunt to the circuit of the microphone m. A call of this kind has
'been used in connection with the Gower telephone.
Fig. 1 of the accompanying drawings illustrates diagrammatically a telephone
circuit operated by alternating currents.
I is a very rapidly working interrupter of the current furnished by an
accumulator battery AC, a coudenser c being introduced in shunt to suppress
sparking.
T is a transformer inducing in the line currents of the desired frequency, t is a
local transformer having a microphone m in its secondary circuit; E is a receiver
of electro dynamometer kind.
Fig. 4 is a vertical section and Fig 5. is a front view of a transmitter. Fig. 6 is
a plan of the upper part.
A is a circular box covered by a thin plate B of wood or ebonite which serves
as the vibrating plate of the microphone.
C is the coil connected to the line.
The microphone consists of 4 lower segments D of carbon not touching each
other, and on them 4 upper carbon segments D¹ not touching each other but lying
on and breaking joint with the lower segments. The vibrations of B cause
variations of resistance to the current passing through the carbons in the usual
way. The combination of the carbons with the coil C constitutes the transformer t
Fig. 1 having a secondary circuit of varying resistance.

page_text: influences, they must have substituted for them pieces made up of fine iron wires
or plates insulated in order to provide against the effects of Foucault currents.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
The herein described method of utilising a single line for multiple telephonic
operation, by sending into the line alternating currents of various frequencies, and
providing a number of transmitter and receiver circuits connected to the line, each
with a condenser of capacity suited to one of those frequencies.
Dated this 31st day of August 1893.
ABEL & IMRAY,
Agents for the Applicants.

page_text: Below the apparatus just described is another circular box E covered by a thin
vibrating plate F and containing a coil G which is connected to the line. The
plate F carries a circular coil H closed on itself. These two coils combined form
an electro dynamometer having parallel circuits. In the circuit of the fixed coil is
included an elastic rod I forming a trembler, on making which act, currents rapidly
interrupted are sent through the coil G, which attracting the coil H causes it and
the plate F to vibrate and sound the call.
Figs. 7 and 8 shew side and front views of the receiver, which is of external shape
like known magnetic receivers, but is really different. The ring J is not a magnet
but simply a handle of any non conducting material such as wood or ebonite. The
receiver itself is like the call instrument just described being a circular box E'
enclosing a fixed coil G' connected to the line and a coil H' closed on itself and
attached to the vibrating plate F¹. This, like the call instrument, forms an electro-
dynamometer having parallel circuits, the action of the one coil on the other
causing vibrations of the plate which reproduce articulate speech.
Fig. 9 represents diagrammatically the connections for the telephone instruments
above described. Like ordinary telephones, there is a suspending hook which
keeps the call in line except during conversation. Tm is the transmitter, R the
receiver C the suspending hook, A the call, B self induction coil, T₁ earth,
c condensers, X trembler or call button. Obviously the arrangements may be
varied so long as the principles illustrated by Fig. 1 are adhered to.
For multiple telephone purposes we adopt the principle illustrated diagram-
matically by Fig. 10. If a condenser c is introduced in the local circuit which
includes the microphone m, and if the capacity of this condenser is such as to
equilibrate the self induction of the system consisting of the line, the receiver E
and the local circuit for a current of period T, with equality of electromotive force,
the intensity of this current will be much greater than that of a current of different
frequency. Now let Fig. 11 illustrate a telephone network containing T a general
transformer inducing in the line alternating currents under the conditions which
are about to be explained,-t¹ t &c. transformers operating the circuits of the
microphones m' m' &c. which include the condensers c¹c &c., E' E &c. are electro-
dynamometer receivers 11 &c. are self induction coils introduced between the
receivers and earth. The arrangement consisting of one microphone transmitter
such as m' its transformer t¹, the general line and the receiver E has a certain self
induction depending on its own construction and also on its relation to the rest of
the network, which self induction, called apparent self induction can be counter-
acted by a condenser c' of suitable capacity; but only for a certain periodicity of
current. If then there are sent into the line alternating currents of various
frequencies such as 10,000, 12,000, &c. which can easily be done by separate
interrupters or vibrators several of them connected simultaneously or successively
to the primary of T one can be chosen, say that of 10,000 frequency to which the
capacity of the condenser c¹ is suited, so that it counteracts the self induction of
the circuit in which it is introduced. The current of 10,000 frequency will then
have in this circuit an intensity much greater than in any of the others, and
consequently the telephone m¹E will operate as if it were alone in the network.
Each of the other circuits being adjusted for a different frequency, will in like
manner operate as if it were alone. As there may be difficulty in precisely
regulating the condensers, it is preferred to send into line not a few currents
differing considerably in frequency such as 10,000, 12,000 &c. but a number varying
between say 9,800 and 10,200, a number between 11,800 and 12,200 and so on, and
thus the condensers, if not regnlated exactly for 10,000 or 12,000, will meet
currents of some frequency near 10,000 or 12,000 to which they are suited.
The arrangements that have been described for telephonic purposes are applicable
also for multiple telegraphy, alternating currents of high tension being employed
with condensers of capacities suited to their frequencies. Where in any of the
telegraphic instruments there are cores or other pieces of iron subject to magnetic