Year: 1887

page_text: Date of Application, 24th Oct.. 1887
Complete Specification Left, 21st July, 1888
Complete Specification Accepted, 24th Aug., 1888
I, JOHN LORIMER CORBETT of 69 Union Street, in the City of Glasgow, Watch-
maker do hereby declare!the nature of this invention to be as follows:-
My invention which relates to improvements in telephonic apparatus has mainly for
its object by increasing in strength and volume in a receiving instrument the
electrical impulses transmitted from a distant sendinginstrument to reproduce specch
and other sounds with great distinctness and loudness.
To that end I introduce a local battery current to reinforce the telephonic
impulses transmitted to the receiver or to increase the magnetism of an electro
magnet in the receiving instrument in any of the following ways the construction of
the receiver being modified accordingly.
Under one modification of my invention the improved telephonic receiver consists
of two coils or bobbins surrounding a core composed by preference of a bundle of soft
iron wires, but which may be a steel bar permanently magnetised, one coil being in
a local battery circuit and the other in the line circuit of the telephone. A diaphragm
of the usual formlor of the improved formation hereinafter described is held in front
of the iron core the parts being fitted in a suitable casing, and the core which is
magnetised by the current flowing through the coil in the line circuit and acts upon
the diaphragm or corresponding device used to reproduce speech or other sounds is
further inagnetised by the current flowing through the coil in the local battery circuit.
The two coils may be placed alongside each other on the core, or one within the
other in the form of an induction coil the strength or volume of the electrical
impulses transmitted through the line circuit being reinforced by the battery current
and enhancing the power of the electro magnet acting on the diaphragm. Or the
core may be enclosed within a coil in the local battery circuit and a coil alongside in
the form of an induction coil having one wire in the telephone circuit and the other
wire being connected to and forming a continuation of the first coil. The central
core forming the electro magnet may or may not be carried through both the single
coil and the induction coil or a separate core may be provided for each and the inter-
action of the coils being utilised either in strengthening the electrical impulses in the

page_text: line circuit to act upon the core or in setting up induced impulses in the battery
circuit to produce the corresponding variations in the magnetism of the core. When
the core is divided in its length each part being surrounded by a coil in the line
circuit. I prefer to fit the coils or bobbins in cup like cases which are placed and may
be secured face to face so as to enclose an air space, the cores being either permanent
magnets or being magnetised by a separate electro-magnet connected to a local
battery. One of the cores or lengths of the core is made tubular or has a tube passed
through it to communicate with said air space, or tubular connections separate from
the core are provided, and on applying the ear to the end of the tube sounds trans-
mitted to the instrument are rendered audible. No diaphragm is required in this
form of the instrument but an ear piece or an air tube may be connected to the
tubular core or other connection to convey sounds to, the desired point and in this
way a single receiving instrument may be connected to several apartments which may
each be provided with a transmitting instrument. In cases in which a diaphragm is
used I prefer to make it of a metallic plate cemented or otherwise secured to the
rim or edge of a disc having a central orifice in which is fitted a tube which may be
connected by air tubing to an ear piece at any convenient point. An air space is
left between the flat part of the disc and the diaphragm within which space may be
fitted a second plate which may be loose or secured at its edge and provided in the
latter case with a central hole. The vibrations communicated to the diaphragm or
inside plate react upon the air within the said space with which the air tubing is
connected, the loudness and distinctness of audible speech received by the instru-
ment being thereby enhanced. In cases in which more than one ear piece is
provided in connection with a single receiver a valve is fitted in each ear piece or in
the connecting tube and is opened by the pressure of the hand, or automatically, in
raising the ear piece, the valve in its normal position being closed.
For convenience in using the receiver the diaphragm and disc are removable from
the part of the instrument containing the electro-magnet and the removable part is
adapted upon being fitted in place to make contact between terminals and complete
the line circuit through the telephone instruments at the receiving station whilst
cutting out the magnets or ringing instrument and upon being removed to break
the circuit through the telephonic instruments and re-establish it through the
magneto.
In lieu of the metallic diaphragm plate I in some cases employ a diaphragm
composed of iron wire gauze whose interstices are filled up with glue, cement or
similar material or composed of mica, paper, wood glass or other inert material,
having loosely fitted or attached to it a wafer like plate or button of iron or a closely
wound spiral spring embedded in cementing material the metallic piece being placed
in proximity to the end of the electro-magnet of the receiver so as to transform the
attractions of the magnet into vibrations of the diaphragm.
The diaphragm may be secured in place by springs or by a plate strung upon
wires or the like and bearing on the central part of the diaphragm which in such
cases is not fixed at the edge or rim and is free to be moved under the springs or
plate. The diaphragm need not be of metal provided the plate bearing on it to secure
it in place be of iron or steel.
In some cases I fit to the diaphragm of the receiver a microphonic transmitter in
the line circuit so that the vibrations of the diaphragm are transformed by the
electrodes of the transmitter into electrical impulses in the battery circuit and react
upon the magnet of a separate receiver which is then employed to receive telephonic
messages.
Dated thin
3
1007
CRUIKSHANK & FAIRWEATHER,
62, Saint Vincent Street, Glasgow,
Agents.

page_text: I. JOHN LORIMER CORBETT of 69 Union Street in the City of Glasgow, Watch-
maker, 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 :-
My Invention which relates to improvements in telephonic apparatus has mainly for
its object by increasing in strength and volume in a receiving instrument the electrical
impulses transmitted from a distant sending instrument to reproduce speech and other
sounds with great distinctness and loudness.
To that end I introduce a local battery current to reinforce the telephonic impulses
transmitted to the receiver or to increase the magnetism of an electro magnet in the
receiving instrument in any of the ways hereinafter described the construction of the
receiver being modified accordingly.
The accompanying drawings illustrate several modifications of my invention.
Under one arrangement represented in longitudinal section at figure 1 and in plan at
figure 2 and in a slightly modified form at figures 3 and 4, the improved telephonic
receiver consists of two coils or bobbins A and B surrounding a core C composed by
preference of a bundle of soft iron wires, but which may be a steel bar permanently
magnetised, one coil B being in a local battery circuit & and the other A in the lino
circuit of the telephone. A diaphragm D of the usual form (or of the improved
formation hereinafter described) is held in front of the iron core C the parts being
fitted in a suitable casing E and the core C which is magnetised by the current flowing
through the coil in the line circuit 7 and acts upon the diaphragm or corresponding
device used to reproduce specch or other sounds is further magnetised by the current
flowing through the coil B in the local battery circuit b. The two coils may be placed
alongside each other on the core as shown or one within the other in the form of an
induction coil, the strength or volume of the electrical impulses transmitted through
the line circuit being reinforced by the, battery current and enhancing the power of
the electro magnet acting on the diaphragm. Or as shown at figures 5 and 6 the
core C may be enclosed within a coil B in the local battery circuit and a coil A
alongside in the form of an induction coil having one wire in the telephone circuit /
and the other wire being connected to and forming a continuation of the first coil B.
The central core C forming the electro magnet may or may not be carried through
both the single coil and the induction coil or as indicated at figure 7 separate
cores C, C, may be provided for the coil B and the induction coil A³ the interaction
of the coils being utilized either in strengthening the electrical impulses in the line
circuit 7 to act upon the core or cores or in setting up induced impulses in the battery
circuit to produce the corresponding variations in the magnetism of the core or
cores. A diaphragm and ear piece may be provided at either or both ends. When
the core C is divided in its length each part being surrounded by a coil in the line
circuit I prefer to fit the coils or bobbins as indicated at figures 8 and 9 in cup like

page_text: cases E which are placed and may be secured face to face so as to enclose an air
space e, the cores being either permanent magnets or being magnetised by a separate
electro magnet connected to a local battery. One of the cores or lengths of the core
is made tubular or has a tube c passed through it to communicate with said air space, or
tubular connections separate from the core are provided; and on applying the ear to the
end of the tube sounds transmitted to the instrument are rendered audible. No
diaphragm is required in this form of the instrument but an ear piece or an air
tube may be connected to the tubular core or other connection to convey sounds to the
desired point and in this way a single receiving instrument may be connected to
several apartments which may each be provided with a transmitting instrument.
In
cases in which a diaphragm is used I prefer to make it as indicated at figures 10
and 11 of a metallic plate D cemented or otherwise secured to the rim or edge of a
disc D having a central orifice d in which is fitted a tube G which may be connected
by air tubing G to an ear piece at any convenient point. An air space is left
between the flat part of the disc D' and the diaphragm D within which space may be
fitted a second plate D2 which may be loose or secured at its edge and provided in the
latter case with a central hole d. The vibrations communicated to the diaphragm D
or inside plate D² react upon the air within the said space d' with which the air
tubing G, G is connected, the loudness and distinctness of audible speech received by
the instrument being thereby enhanced. In cases in which more than one ear piece
is provided in connection with a single receiver a valve is or may be fitted in each ear
piece or in the connecting tube and is opened by the pressure of the hand, or auto-
matically, in raising the ear piece, the valve in its normal position being closed.
For convenience in using the receiver the diaphragm and disc are made removable
from the part of the instrument containing the electro-magnet and the removable
part D, as indicated at figures 12 and 13, is or may be adapted upon being fitted in
place to make contact between terminals, l, and complete the line circuit through
the telephone instruments at the receiving station whilst cutting out the magnet or
ringing instrument by means of a non-conducting knob 63 serving to break contact
between terminal springs b', 6' connected to said instrument and upon being removed
to break the circuit through the telephonic instruments and re-establish it through
the magnet.
In lieu of the metallic diaphragm plate I in some cases employ a diaphragm such
as is represented at figure 14 composed of iron wire gauze whose interstices are filled
up with glue, cement or similar material or as indicated at figure 15 composed of mica,
paper, wood, glass or other inert material, having loosely fitted or attached to it a
wafer like plate or button of iron or a closely wound spiral spring I embedded in
cementing material the metallic piece being placed in proximity to the end of the
eloctro-magnet of the receiver so as to transform the attractions of the magnet into
vibrations of the diaphragm.
The diaphragm may be secured in place by springs or as indicated at figure by a
plate strung upon wires or the like and bearing on the central part of the diaphragmn
which in such cases is not fixed at the edge or rim and is free to be moved under the
springs or plate. The diaphragm need not be of metal provided the plate bearing on
it to secure it in place be of iron or steel.
In some cases I fit to the diaphragmn of the receiver a microphonic transmitter in
the line circuit so that the vibrations of the diaphragm are transformed by the
electrodes of the transmitter into electrical impulses in the battery circuit and
react upon the magnet of a separate receiver which is then employed to receive
telephonic messages.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what I
claim is :-
1. In a telephonic receiving instrument the employment in conjunction with a coil
in the line circuit of a coil or coils in a local battery circuit substantially as and for
the nuenose sat farth

page_text: 2. A telephonic receiving instrument constructed under any of the several modifi-
cations hereinbefore described with reference to the accompanying drawings.
3. A diaphragm for a telephonic receiving instrument composed of wire gauze
whose interstices are filled up substantially as described.
4. A diaphragm for a telephonic receiving instrument composed of inert material
having a central button plate or piece of metal adapted to be acted on by the magnet
of the instrument substantially as described.
n. This funt dave of Tul. 1000
CRUIKSHANK & FAIRWEATHER,
62, Saint Vincent Street, Glasgow,
Agents.