AN IMPROVED SYSTEM OF TELEPHONIC TRANSMISSION as
Year: 1884

page_text: I ALEXANDER MELVILLE CLARK of the firm of A. M. and Wm Clark of
53 Chancery Lane in the County of Middlesex, Fellow of the Institute of Patent
Agents do hereby declaro the nature of the said invention for "AN IMPROVED
SYSTEM OF TELEPHONIC TRANSMISSION (A communication to me from abroad by
Louis Maiche of Paris, France,) to be as follows :-
"
This Invention relates to an improved system of telephonic transmission which
consists essentially in the use in lieu of earth of a telegraph wire in service for
telegraphic purposes without causing any interference between the concurrent
action of the telephonic and telegraphic services.
I install at each end of a telephonic line a microphonic station, such as the
Maiche electrophone for example, and instead of completing the circuit through
earth or by a special return wire, I complete it by passing it through a resistance (a
suitable rheostat) and from this rheostat I connect it to a telegraphic wire in uso.
A switch is provided whereby to cut out the resistance of the rheostat when
transmitting and to restore it when receiving, a spoken message.
In order that the Invention may be more readily understood I have illustrated
in the annexed drawings an example of a telephonic installation in accordance
with this Invention.
Figure 1 is a diagram of the telephonic line connecting Paris and Versailles, the
return wire being the telegraphic wire connecting Paris and Chartres.
Figure 2 shows details of the Switch for altering the circuit according as the
telephonic message is being transmitted or received as hereafter explained.
A is the transmitter, an electrophone for instance; B is the telephone receiver,
C is the resistance above referred to, D the telegraphic instruments and E the
switch shown in figure 2 and F is the telephonic battery. When speaking the
switch key e is pressed down on the contacts e¹ e³ under which circumstances the
telephonic current acts in the ordinary way. When listening the key is not
pressed down and the contact at e¹ e² being broken, the current passes through the
resistance C and the telephone B to the line wire. In this case the derivations
due to the telegraphic service are sufficiently reduced to be inaudible and the same
is the case with the ordinary induction which is annulled' 1st by the action of the

page_text: return wire acting as a double conductor 2nd by the resistance met with in
traversing rheostat C whereby the induction currents are lost to earth by derivation
by the telegraph posts.
The tension of the telephonic current is so regulated as to enable it to overcome
the resistance whilst reducing the derivations as much as possible, which cannot
fail to be the case since the telephonic current meets with less resistance in the
rheostat coil than it would meet with in order to become lost by derivation on
the line.
The switch figure 2 is so arranged that when the knob e of the spring arm E is
pressed down its contact presses on that of the spring pallet e¹ which in turn
presses on the contact stud e² and this is the position when speaking, the current
then passing directly to the line. When the pressure is removed from the switch
it assumes the position figure 2 and the terminals being respectively connected as
indicated in this figure it will be seen that the primary wire of the induction coil
being broken the current arriving cannot act on it inductively and therefore acts
on the receiver without causing the microphone to speak.
Moreover this arrangement avoids useless wear of the battery when listening in
consequence of the temporary interruption of the primary wire at this time.
The arrangements here indicated may be varied without departing from the
invention for example the transmitters, receivers, batteries and accessories may be
of any suitable kind and the switch E may be constructed in any way whereby
the communications above indicated between the line, the resistance and the
primary wire of the transmitter coil may be effected.
It should also be mentioned that the nature and value of the resistance C
depends upon the length of the line and the other conditions of the installation.
Dated this 7th day of March 1884.

page_text: I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of
53, Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, do hereby declare the nature of the said Invention for "AN IMPROVED
SYSTEM OF TELEPHONIC TRANSMISSION" (a communication to me from abroad by
Louis Maiche of Paris, France,) 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 an improved system of telephonic transmission which
consists essentially in the use in lieu of earth of a telegraph wire in service for
telegraphic purposes without causing any interference between the concurrent'
action of the telephonic and telegraphic services.
I instal at each end of a telephonic line a microphonic station, such as the Maiche
electrophone for example and instead of completing the circuit through earth or by
a special return wire, I complete it by passing it through a resistance (a suitable'
rheostat) and from this rheostat I connect it to a telegraphic wire in use. A'
switch is provided whereby to cut out the resistance of the rheostat when.
transmitting and to restore it when receiving, a spoken message.
In order that the invention may be more readily understood I have illustrated in
the annexed drawings an example of a telephonic installation in accordance with
this invention.
Figure 1 is a diagram of the telephonic line connecting Paris and Versailles, the
return wire being the telegraphic wire connecting Paris and Chartres.
Figure 2 shows details of the switch for altering the circuit, according as the.
telephonic message is being transmitted or received as hereafter explained.
A is the transmitter, an electrophone for instance, B is the telephone receiver,.
Cis the resistance above referred to, D the telegraphic instruments and E the switch
shown in figure 2 and F is the telephonic battery, that is to say the battery in
the circuit of which are placed the primary wire of the transmitter coil and
the telephonic transmitter microphone or equivalent device. When speaking, the
switch key e is pressed down on the contacts e¹ es, under which circumstances the
telephonic current acts in the ordinary way. When listening, the key is not
pressed down and the contact at ele being broken, the current passes through the
resistance C and the telephone B to the line wire. In this case the derivations due
to the telegraphic service are sufficiently reduced to be inaudible and the same is
the case with the ordinary induction which is annulled 1st by the action of the
return wire acting as a double conductor 2nd by the resistance of the rheostat C,
whereby the induction currents are lost to earth by derivation by the telegraph
poles.
The tension of the telephonic current is so regulated as to enable it to overcome
the resistance, whilst reducing the derivations as much as possible, which effect
cannot fail to be produced, since the telephonic current meets with less resistance
in the rheostat coil than it would meet with in order to become lost by derivation
on the line.
The switch figure 2 is so arranged that when the knob e of the spring arm E is
pressed down, its contact presses on that of the spring pallet e' which in turn
presses on the contact stud e and this is the position when speaking, the current
then passing directly to the line. When the pressure is removed from the switch
it assumes the position figure 2 and the terminals being respectively connected as
indicated in this figure, it will be seen that the primary wire of the induction coil

page_text: being broken, the current arriving cannot act on it inductively and therefore acts
only on the receiver, without causing the microphone to speak.
"
In the telephonic transmitter or electrophone A figure 1, P indicates the
terminals of the battery, T the terminals of the telephone receiver and L the line
terminals.
Moreover this arrangement avoids useless wear of the battery when listening in
consequence of the temporary interruption of the primary wire at this time. The
arrangements here indicated may be varied without departing from the invention,
for example the transmitters, receivers, batteries and accessories may be of any
suitable kind and the switch I may be constructed in any way whereby the
communications above indicated between the line, the resistance and the primary
wire of the transmitter coil may be effected.
It should also be mentioned that the nature and value of the resistance C
depends upon the length of the line and the other conditions of the installation.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed I declare that what
I claim is
1st In a telephonic installation, the employment as a return wire of a
telegraphic wire in service: by the interposition in the line wire of a properly
calculated resistance which the telephonic currents from the transmitting station
are caused to traverse before returning by the said wire, essentially as herein
specified.
2nd In a system of telephonic transmission, wherein an ordinary telegraph wire
in service is used as a return circuit, the combination with the telegraphic and
telephonic apparatus A, B, D and their adjuncts, placed in circuit in the ordinary
way, of a resistance C and a switch E suitably arranged to enable the said
resistance to be introduced in the line circuit during the reception and to be cut
out during the transmission of a telephonic communication, the whole arranged to
operate substantially as and for the purpose specified.
3rd In combination with the telegraphic and telephonic apparatus A B D, the
battery F, the resistance C and all necessary accessories, the switch E provided
with contact e, pallet c and contact e³, communicating as herein described in
reference to figuro 2, for the purpose specified.
Dated this 5th day of December 1884.