An Improved Loud Speaking Telephone and Circuits for same.
Year: 1893

page_text: Date of Application, 26th June, 1893
Complete Specification Left, 25th Apr., 1894-Accepted, 23rd June, 1894
PROVISIONAL SPECIFICATION.
An Improved Loud Speaking Telephone and Circuits for same.
I ALFRED GRAHAM of 32 De Crespegny Park Denmark Hill in the County of
London Electrician do hereby declare the nature of this invention to be as
follows:-
The objects of my invention are to reproduce the speaking voice in the telephone
receiver more clearly and loudly than has been done hitherto and at the same time
to do away with the necessity for holding the receiver to the ear and thus to reduce
the expense and complexity of the apparatus used and save the trouble of its
employment. 1 also simplify and cheapen the telephone by doing without any bell
or other apparatus for calling attention. I also make a transmitter with a circuit
closing key working automatically in the hand of the speaker. While I further
arrange my circuits on a simple system adjusted for working in large buildings with
a moveable contact maker.
To effect these objects I arrange a combination of new telephone transmitter and
receiver in a novel manner and I work them by direct circuit upon the single wire
system or by a direct and separate circuit upon a new method of separate wires
arranged upon a novel system of circuits and acting with a moveable contact
maker.
My apparatus consists of a transmitter and galvanic battery at one end of the
line in the same and direct circuit with the line wire and a telephone receiver at
the distant end of this same line. In order to get the reverse action I use another
set of apparatus with another separate line in direct circuit merely reversing the
positions of transmitter with battery and telephone receiver. The result of this
system of a separate wire each way is to obtain a clearer and stronger reproduction
of the voice in the receiver by the saving of force and reduction of resistance but I
can also use the direct circuit upon the single wire in the ordinary way of arranging
telephone apparatus.
The telephone transmitter I use is made with a circuit closing key which is
operated by the hand of the holder pressing a moveable knob and which when
released returns automatically by means of a spring thereby breaking the circuit
again and having it open until again closed in the same way.
The receiver I employ is one provided with a diaphragm of large diameter and it
need not be held to the ear but fixed to a wall or otherwise arranged.
I am aware that the system of working with a direct current upon a single wire
is not new but it has only been used hitherto in conjunction with a receiver of
small size which has to be held close to the ear in order that the voice of the
speaker may be heard at all and it thus necessitates a tube or cord and other
apparatus.
By the use of a receiver with a diaphragm of large diameter and the system of
working in direct circuit I obtain a louder and clearer reproduction of the speakers
voice than can be got in any other way and as that voice speaks out of the receiver
into the room it would be heard by anyone there without being first called by a bell
and without the need of applying the receiver to the ear to listen, as is necessary in
all other systems.
My invention can be used for a single telephone and it can be adapted for use in
large buildings in which case I fit in each of the rooms the above mentioned
telephonic transmitter operated by the hands of the user and also a commutator or
moveable contact maker which is essential for the purpose of placing the transmitter

page_text: in circuit with any of the wires and also a telephone receiver with large diaphragm
as above described.
In connection with each receiver I arrange a line wire so that any one of the
rooms on the system may be able to make connection with this said line wire by
means of the commutator or moveable contact maker-the transmitter in each room
is arranged in connection with this said commutator or moveable contact maker
and closes the circuit with itself and a galvanic battery by means of its circuit
closing key.
When the necessary contact is made by the commutator or moveable contact
maker the transmitter is used to close the circuit on the particular line
required.
The new and useful features of my invention are therefore, amongst others, the
following,
1. The combination and use of a receiver with a diaphragm of large diameter in
direct line circuit with a carbon or other transmitter and battery upon the single
line method.
2. The system of direct circuit upon a separate line wire having a battery and
transmitter at one end of the line wire and a receiver with a diaphragm of large
diameter at the other end.
3. In a system of telephonic communication the combination of a telephone
transmitter and circuit closing key.
4. The use of a separate line wire in direct communication with each of the
receivers on the system.
5. The combination of a commutator or moveable contact maker in conjunction
with the transmitter and receiver and the system of circuits.
Dated the 26th day of June 1893.
ALFRED GKAHAM,
COMPLETE SPECIFICATION.
An Improved Loud Speaking Telephone and Circuits for same.
I, ALFRED GRAHAM of No. 32 De Crespigny Park, Denmark Hill, in the
County of London, Electrician, 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 objects of my invention are, first, to reproduce the speaking voice in the
telephone receiver more clearly and loudly than hitherto and at the same time to
avoid the necessity of holding the receiver to the ear, secondly, to simplify and
cheapen the apparatus, thirdly, to construct a transmitter in combination with a
cucuit controller which can be conveniently operated by the same hand which
holds the instrument, and, fourthly, to provide means for connecting together a
number of telephone stations so that there may be inter-communication without the
necessity of an exchange or similar switchboard and without the possibility of
conversation being overheard at other stations.
To effect these objects I arrange a combination of transmitter and receiver in a
novel manner and work them by direct circuit upon the single wire system or by
a direct and separate circuit upon a new method of separate wires arranged upon
a novel system of circuits and acting with a movable contact maker.
My apparatus consists of a transmitter and galvanic battery at one end of the
line in the same and direct circuit with the line wire and a receiver at the distant
end of this same line. In order to attain the reverse action I use another set of
apparatus with another separate line in direct circuit merely reversing the positions
of transmitter with battery and receiver. The result of this system of a separate
wire each way is to obtain a clearer and stronger reproduction of the voice in the
receiver by the saving of force and reduction of resistance but I can also use

page_text: pparatus.
In the accompanying drawings
Fig. 1 shows a transmitter, and Fig. 1
according to my invention;
shows in section a receiver constructed
Fig. 2 illustrates diagrammatically a system of four stations embodying my
invention;
Fig. 3 illustrates a system wherein only one battery is employed;
Fig. 4 illustrates the simplest form of my invention, and
Fig. 5 is a detail hereinafter referred to.
Referring to Fig. 1 the transmitter 1 employ has secured to the rear of its body
a knob A of insulating material recessed as at a so as to form when in position an
enclosed chamber. In this chamber is located the head of a screw B and a metallic
spring C one end of which is secured to the body of the instrument while the other
end passes over, but is not in contact with, the screw B. Passing through the
knob A. and entering the enclosed chamber is a circuit closing key or plunger D
whose inner end rests upon the free end of the spring C, its outer end terminating
in a button d. One conducting wire is connected to the spring C while the other
wire is connected to a plate e which is in electrical connection with the diaphragm
of the instrument.
The receiver I employ is one provided with a diaphragm of larger diameter
than hitherto generally used and when so constructed and arranged as herein
described such instrument need not be held to the ear but may be affixed to a wall
or the like.
The
The receiver is constructed as shown in Fig. 1^. M is the diaphragm held
in a suitable case N to which is attached the trumpet P. The centre of the
diaphragm is hollowed out on each side as shown at m and its edge part is clamped
in the case N. R is a U-shaped magnet which is permanently magnetised and
which carries upon its polar extremities two spools S, S of low resistance.
instrument is intended to operate with a quantity current and the magnetic field is
a relatively intense one. The circuit 1-2 through the low resistance spools
is intended to be a battery circuit with which the transmitter is directly connected
furnishing a quantity current which passes through the receiver coils
distinguished from the tension current by the induction coils ordinarily employed.
My receiver, however, is also capable of being used with an induction current
produced by a reversed induction coil and giving quantity currents in the receiver
circuit.
as
According to my invention the receiver of each station is placed in an independent
circuit, each station being in connection with the remaining stations of the system
so that any one of the transmitters may be connected with any one of the receivers
without including in the circuit the receiver of any other station. Each receiver
being in an independent circuit there will be connected with this circuit when in
operation only the transmitter, receiver, and the battery to supply the current.
This enables the effective employment of loud speaking telephones so that no call
bells are required.
Referring to Fig. 2, A, B, C, D, are four line wires with which are connected
receivers a, b, c, d. These receivers are connected with the wires at the
stations 1, 2, 3, 4, to which all wires run. The common return wire E connects all
the receivers together. At each station is a transmitter c connected through the
E.
normally open circuit controller and battery 9 to the common return wire,
The other terminal of each transmitter is connected to a movable contact maker A¹
adapted to connect any one of the three contacts. The contacts at each station are
connected, as shown, to the three line wires to which the receivers of the other
stations are connected.
In Fig. 3 is shown a similar arrangement to that in Fig. 2 except that in place
of the single return wire E two return wires E and F are employed and a single
battery g is placed between them.

page_text: In Fig. 4 a simple system of two stations is shown. Two batteries
employed or a single one may be placed in the common return.
g may be
may sometimes provide at each station an additional silent receiver as shown
in Fig. 5. This instrument I may be hung upon a switch hook K playing between
two contacts and k, and when so hung the loud speaking receiver will be in
circuit but upon the removal of the instrument I the loud speaking receiver will be
cut out of circuit and the circuit closed through the silent receiver. This
arrangement is of use when it is desired to carry on a conversation which is not
intended to be overheard.
I believe it is not new to work with a direct current upon a single wire but so far
as I am aware it has only been used hitherto in conjunction with a receiver of
small size necessitating its being held close to the ear. By the use of a receiver
provided with a diaphragm of large diameter in combination with the system
of working in direct circuit I am enabled to obtain a louder and clearer reproduction
.of voice.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a telephone transmitter, a case terminating in a knob in combination with
a circuit controller operated by a plunger passing through such knob and capable
of being actuated by the hand grasping the knob substantially as set forth.
2. The combination, in a telephone system, of the receiver as herein described,
a transmitter, and a battery either in direct circuit upon a single wire or so arranged
that the said transmitter and a receiver are each upon a direct and separate circuit
substantially as set forth.
3. In a telephone system having two or more stations, placing each receiver in
an independent circuit substantially as set forth.
4. In a telephone system having three or more stations, the combination of a
separate line wire for each receiver of each station extending to the two or more
other stations, with transmitters at the several stations, and a circuit controller at
each station for connecting the transmitter of that station with the receiver of any
one of the other stations substantially as set forth.
5. In a telephone system having three or more stations, the combination of the
separate line wire for each receiver of each station extending to the two or more
other stations, with transmitters at the several stations, and a circuit controller at
each station for connecting the transmitter of that station with the receiver of any
one of the other stations, and the normally open circuit-closer in the transmitter
circuit at each station substantially as set forth.
6. In a telephone system having two or more stations, the combination, with
independent receiver wires, of a battery common to two or more wires substantially
as set forth.
7. In a telephone system having two or more stations, the combination, with a
loud speaking receiving instrument, of a silent receiver and means for substituting
it for the loud speaking receiver in the circuit substantially as set forth.
Dated this 25th day of April 1894.
A. F. SPOONER,
124, Chancery Lane, W.C., Agent for the Applicant.