Improvements in Electric Telephony and Telegraphy.
Year: 1894

page_text: Date of Application, 10th Jan., 1894
Complete Specification Left, 8th Nov., 1894-Accepted, 8th Dec., 1894
PROVISIONAL SPECIFICATION.
Improvements in Electric Telephony and Telegraphy.
We, ALEXANDER MUIRHEAD, Electrical Engineer, and GEORGE WILLIAM
GREEN, Civil Engineer, both of 2 Princes Street Westminster S.W. do hereby
declare the nature of this invention to be as follows:-
This invention has for its object the increase of the loudness of telephonic
transmission, and relates further to the circuit arrangements, and combination
of parts whereby certain telegraphic signals can be transmitted in connection
therewith.
In carrying out our invention we employ at each telephone station a transformer
with open magnetic circuit having two primary and a single secondary circuit
wound concentrically on a core of iron wires.
In the circuit of one of the primary wires we place a transmitter, preferably
one of the granular carbon form, and battery; in the other primary circuit the
receiver with coils of low resistance and a diaphragm of large diameter, the
secondary circuit of the transformer being connected to the line and return wires.
The transformer may be wound with more than two primary wires for cases
in which a number of receivers have to be included in the same circuit.
Sometimes we place the transmitter, battery and receiver in the same primary
circuit in which case the transmitter with battery and a key or switch are joined
up parallel with the receiver and the primary wire.
At intermediate points on the line we sometimes place a transformer con-
structed in the manner above described with the secondary either continuous
with the line circuit or between the line wire and the return wire or earth.
When it is required to transmit the same messages to a number of stations
at the same time we wind a corresponding number of secondary circuits on the
transformer.
In order to call up a correspondent on our system of telephonic transmission
the transmitter is placed in front of the receiver and then the battery circuit
of the transmitter is closed, the result being a loud continuous vibration set up
in the receivers at both ends of the line.
With the transmitter thus placed in front of the receiver messages can be
transmitted in a loud and effective manner by operating the key in the battery
circuit according to the Morse code.
ALEX. MUIRHEAD.
GEO. W. GREEN.
COMPLETE SPECIFICATION.
Improvements in Electric Telephony and Telegraphy.
We, ALEXANDER MUIRHEAD, Telegraph Engineer, and GEORGE WILLIAM
GREEN, Civil Engineer, both of 2 Princes Street, Westminster, S. W., 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:-
Our invention has for its object the increase of the loudness of telephonic
transmission and relates further to the circuit arrangements, and combination

page_text: of parts whereby certain telegraphic signals can be transmitted in counection
therewith.
In order that our invention may be more clearly understood reference is
hereafter made to the accompanying drawing which is a diagrammatic illustration.
In carrying out our invention we employ at each telephone station an induction
coil or transformer P.S. with open magnetic circuit having a plurality of primary
circuits and a single secondary circuit wound concentrically on a core of iron wires.
The diagram shows an arrangement of three primary circuits of the transformer
in one of which (say P¹) we place a telephone transmitter T, which is preferably
one of the granular carbon type with thin diaphragm, with a contact key K and a
battery B. In another primary circuit (say P1) we include an ordinary Morse
key M.K. with battery B'. In the third primary circuit P is included the
telephone receiver R with coils of low resistance and a diaphragm preferably of
large diameter. The secondary circuit S of the transformer is connected to the
line and earth or return wire.
At intermediate points on the line we may place a transformer constructed in the
manner hereinbefore described with the secondary circuit either continuous with
the line wire as shown at X or between the line wire and the return wire or earth
as shown at Y.
When a number of telephone receivers are required to be included in the same
circuit the transformer is wound with a corresponding extra number of primary
circuits.
When it is desired to transmit the same messages to a number of stations
at the same time we wind a corresponding number of secondary circuits on the
transformer.
By the employment and disposition of apparatus as herein described our system
is adapted to transmit and receive telegraphic as well as telephonic signals. In
order to call up a correspondent or to produce audible telegraphic signals at a
distant station, the telephonic transmitter T is placed with its diaphragm near, or
in front of, or in a position relative to that of the receiver R and, the transmitter
circuit being closed by the key K, reciprocal effects are produced between the
diaphragms of the transmitter and receiver respectively resulting in the emission from
the receiver of a loud and continuous sound. When not in use for talking purposes
the transmitter will be supported with its trumpet opposed to that of the receiver
as illustrated in the drawing. To call the distant station it is only necessary to
close the circuit at the key K when the reciprocal action between the receiver
and transmitter will be set up and a sound will be produced in the receivers at both
ends of the line. A return signal having been given the transmitter and receiver
can then be employed for carrying on conversation over the telephone line, the
movable instrument (whether transmitter or receiver) being removed from its
indicated position and returned thereto after the conversation is completed. By
the aid of the Morse key M.K. and the additional circuit P' messages can be sent
through the system in accordance with the Morse code the signals producing an
audible and readily distinguished clicking in the receiver diaphragm and this may
be continued at the same time as and without unduly disconcerting the speech
transmission.
The diaphragms of the carbon transmitters used by us are made preferably
either of a thin disc of carbon or of a thin sheet of glass at the centre of which a
smaller carbon disc is firmly attached by means of shellac or other cementing
material, in the latter case contact being made with the carbon disc by a strip of
tinfoil or other thin conducting material. These diaphragms are made considerably
larger than those now generally in use. We have found that with iron diaphragms
a diameter of about four inches and thickness of metal of about 025 inch or
with carbon diaphragms a diameter of about three inches and about 02 inch in
thickness, very loud effects can be produced.
Sometimes instead of the usual iron diaphragm we employ in the construction of
the receivers thin glass diaphragms to which a disc of iron is attached.

page_text: We believe it is not new in an electric telephone system to place the receiver in
the primary circuit of an induction coil or transformer and to connect the secondary
circuit thereof to the line wire, and we do not claim such as our invention, but
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is ;-
1. A system of electric telephony and telegraphy having in combination at each
station a transformer wound with three primary circuits in one of which is a
receiving instrument in another a transmitter and in a third a Morse key, and a
secondary circuit connected to the line wire.
2. A system of electric telephony and telegraphy having in combination a
plurality of primary circuits in one of which is a transmitter in another a Morse
key and in each of the remaining ones a receiving or other instrument, and a
secondary circuit connected to the line wire.
3. A system of electric telephony and telegraphy having in combination a
plurality of primary circuits containing respectively a Morse key a transmitter and
one or more receiving or other instruments, and a plurality of secondary circuits
connected one to each line wire.
4. In a system of electric telephony and telegraphy placing a transmitter and a
receiver, which are in separate circuits inductively connected with each other, in
such a position relative to each other that upon completing the battery circuit a
continuous audible sound is produced.
5. In a system of electric telephony and telegraphy the means, substantially as
described, whereby telegraphic and telephonic impulses may be continued at the
same time without unduly disconcerting each other.
Dated this 8th day of November 1894.
A. F. SPOONER,
124, Chancery Lane, W.C., Agent for the Applicants.