IMPROVEMENTS IN TELEPHONES AND THEIR CONNECTIONS
Year: 1879

page_text: LETTERS PATENT to John Imray, of No. 28, Southampton Buildings, Chancery
Lane, in the County of Middlesex, for the Invention of "IMPROVEMENTS IN
TELEPHONES AND THEIR CONNECTIONS." A communication from abroad by
Joshua Franklin Bailey, of New York, United States of America.
COMPLETE SPECIFICATION filed by the said John Imray at the Office of
the Commissioners of Patents on the 16th December 1879.
JOHN JMRAY, of No. 28, Southampton Buildings, Chancery Lane, in the County
of Middlesex. "IMPROVEMENTS IN TELEPHONES AND THEIR CONNECTIONS." A
communication from abroad by Joshua Franklin Bailey, of New York, United
States of America.
This Invention relates to telephones of the kind in which a current from a
battery in passing through the transmitter undergoes variations resulting from
action on an imperfect conductor such as carbon, by a membrane or diaphragm
caused to vibrate by sound pulses. I will describe the improvements in such instru-
ments according to the present Invention, referring to the accompanying Drawings
and the figures and letters marked thereon. Fig. 1, Sheet I., is a plan under the
diaphragm, and Fig. 2 is a vertical section on M, N, of a transmitter. A is the
casing, fixed on an arm or bracket B, and having a cover C carrying the mouth
piece and secured to the casing by screws c. The diaphragni, preferably of metal,
is secured between the casing and its cover with insulating rings d at its edge on
each side. One or several carbon discs e, e', e³, held in a ring F¹ of vulcanite or
other non-conducting material rest on the head G of a pin g, which is free to slide
in a hole at the bottom of the casing. A stud & resting on or inserted in the
carbon e bears against the diaphragm. A spring H screwed at one end h to the
casing and held at the other end by an adjustable setting screw h¹ has in its middle
a slotted hole through which passes the pin g. By means of the screw h¹ the force
with which the spring H presses the stud d against the diaphragm can be adjusted
as desired without risk of breaking the carbons. One wire of the circuit being
connected to the casing A, and the other to the insulated connection I, the current
TDS37

page_text: passes through the casing, the pin g, and its head G, and through the 'carbons and from
the upper carbon by a wire i to the connection I to the other wire. The receiving
instrument may be of any known kind.
The diaphragm
The
Fig. 3, Sheet I., shews a modified arrangement of transmitter.
consists of two metal plates a, a¹, holding between them a thin layer b of felt,
leather, or such like material. The plates are held by a central screw c to the
support d, to which one of the wires fis connected. The upper part of d forms a
bracket carrying the setting screw 9, which bears upon the carbon j, held in a
spring h, which is connected to the wire . Fig. 4, Sheet I., shews to an enlarged
scale a mode of adjusting the carbon to the vibrating diaphragm. To the centre
of the diaphragm a is fixed by a small bolt e an arm d of vulcanite or other non-
conductor. The carbon f rounded off at both ends is loosely fitted in a hole in d,
and is pressed by a spring g against the head of the bolt e. The spring g, which
can be adjusted by the screw v, carries at its free end a mass of copper k.
circuit is connected by a strip of copper to e, and in like manner at n to the screw 2. 1
Figs. 5 and 6, Sheet I., shew respectively a section and a plan of a microphonic
telephone capable of transmitting very faint sounds. A is a resonant box carrying
the diaphragm p, on which rests a piece n of finely divided compressed material
such as carbon. A similar piece m is placed under a lever c pivotted at x, and
counterbalanced by an arm h with adjustable weight i. By means of a light spring
e and sliding pin f the pressure on the pieces m, n, can be adjusted. A light plate k
which may be of mica attached to the lever c forms a bottom to the mouth piece B.
Extremely faint sounds so vary the pressure of the pieces m, n, and their electrical
resistance as to make considerable variations in the electric current which passes
from 3 to 4 through p, n, m, o, communicating these to the receiving instrument at
a distance. This instrument can be used without an induction coil in the circuit.
Fig. 7, Sheet I., shews diagrammatically a mode of connecting the transmitting and
receiving instruments. Fig. 8, Sheet I., is a section shewing a modified form of
transmitter, part of which is shewn to an enlarged scale at Fig. 9, 'Sheet I. A
resonant box a is fitted with a diaphragm b secured by rings and screws c. There
may be several contacts with the diaphragm of these three, marked 1, 2, and 3, are
shewn in Fig. 7, and two marked 1 and 2 in Fig. 8. These are connected to the
circuit in such a manner that the electric condition is influenced by variations of
voice, and consequently the electro-magnet h at the receiver causes vibrations at
the diaphragm b corresponding with the strength of sound at the transmitter.
Referring to Fig. 7 one pole of the principal battery M, B, is connected to earth,
and the other to the diaphragm b. The line wire is connected through rheostats
R, R¹, R³, with the several contact springs i, which very nearly bear against the
diaphragm, being kept just off it by the retracting screws k The point 2 closes
the circuit for the most faint sounds, being connected through the rheostat R¹ of
highest resistance. For stronger vibrations the circuit is closed at 1 through the
rheostat R of less resistance, and for still stronger vibrations the circuit is closed at
3 through the rheostat R³ of least resistance. Thus according as weaker or stronger
pulses act on the diaphragm currents of less or greater strength are transmitted to
the receiver. The electro magnet u connected to earth through a rheostat R³ serves
to neutralise the permanent charge of the line and the induction belonging to the
instruments. At the receiver the armature m is a spring blade held at each end n;
its middle is connected to the diaphragm and it is caused to vibrate by the action
of the electro-magnet h. This form of armature is preferable to one that oscillates,
and its motion is so limited that it does not touch nor adhere to the poles of the
magnet. As shewn in Fig. 8 the battery B is interposed between the adjusting
screw v and the supports of the spring r, and the battery B¹ is in like manner
interposed between v¹ and the support 8' of the spring ¹, the screws and v¹
being insulated from the springs, but included with 8, 8, in the circuit from line?
to earth G. During quiescence of the instrument these batteries are short circuited
through r, m³, and r¹, and consequently either acts on the line only when the

page_text: diaphragm vibrates, the contact with 1 or 2 being then broken, or when the contact
with both is broken both batteries charge the line, the force of current being thus
increased when the sound acting on the diaphragm is increased.
In this manner
three or more diaphragm contacts with their respective batteries may be arranged.
The tension regulator is of a special construction. It consists of several compart-
ments containing fluid conductors, which are insulated from each other except when
they meet at a narrow aperture. In each compartment there is an electrode, and
the diaphragm or other body caused to vibrate by sound pulses regulates the area
of the aperture or the pressure in such manner as to vary the electric tension in
the line in correspondence with the sonorous vibrations. Fig. 10, Sheet I., is a
vertical longitudinal section, and Fig. 11 is a transverse section on x, x, of a trans-
mitter provided with this apparatus. B is a non-conducting cylinder divided by a
partition b into two compartments filled with conducting fluid, in each of which
there is an electrode, the one connected to the line and the other through a battery
to earth. Through the partition b there is a passage p, through which the fluid in
the two compartments communicates. On the front of the cylinder is a plate e of
mica, caoutchouc, or other non-conductor held on by a cap c having a central slot;
in front of this is a box h with mouth piece A and a diaphragm i on which is a
piece of cork t entering the slot of the cap and bearing against the plate e. The
diaphragm i and cork t are so adjusted as to make the passage p very narrow, but
when the diaphragm is caused to vibrate by sound pulses the passage is increased
and diminished proportionally to the extent of each vibration, and there are
proportional vibrations of resistance to the electrical current passing from the one
compartment to the other, and therefore to the tension in the line. Apparatus on
this system may have various forms. In Fig. 16, Sheet I, the cylinder is shewn
vertical, in which case the diaphragm e and cap c are dispensed with. In Fig. 12,
Sheet I., there are several passages through the partition b governed by a thin slide d
having corresponding passages and pressed against the partition by a spring o; this
slide is moved by the vibrations of the diaphragm i so as more or less to open and
close the passages through b. In Fig. 13, Sheet I., the division of B into compart-
ments is shewn to be made by a horizontal partition b having an aperture governed
by a valve connected to the diaphragm i. In the arrangement shewn at Fig. 14,
Sheet I., the passage between the compartments B, B, is through a flexible tube m
acted on by a stem n connected to the diaphragm i. For charging the compart-
ments mercury may be employed instead of an electrolytic liquid and porous
material such as paper may form the connection between the portions of fluid in the
two compartments, as shewn at Fig. 15, Sheet L, where 8, 8, is a strip of paper or
porous fabric dipping into the fluid at both ends, and pressed on in the middle by
a piece p attached to the diaphragm i with more or less force as the diaphragm
vibrates to and fro. Fig. 17, Sheet I., shews a modified arrangement for holding
the carbons referred to in relation to Fig. 3. A small tube a of caoutchouc or other
non-conductor is inserted in a hole in the support. The thin disc 6 of carbon is
placed in the bottom of the hole resting on a convex disc of platinum c; on b is
placed a double convex piece of platinum d, and on this is placed the second carbon
e. Fig. 18, Sheet I., shews to a small scale an arrangement of mouthpiece providing
large space for concentrating the sound pulses, the form of the tube and the
horizontal position of the diaphragm preventing injury from moisture.
Fig. 1, Sheet II., shews diagrammatically an arrangement for telephonic
communication between a transmitting station V and a distant receiving station.
In the transmitter A. the metallic plate a rests by its tube on the diaphragm C,
which is connected to the induction coil I, as also is the plate e, B being the
battery. Between the plates cand e is a disc of felt, round which a strip of
platinum is wound many times; the contact of c with this platinum is varied by
the vibrations of the diaphragm, the pressure on the platinum being regulated by
an adjusting screw acting on e and compressing more or less the felt. At R there
is a receiver, from which, by means of flexible tubes, the sounds are conveyed to

page_text: the ears.
At the receiving station A¹ is a polarised magnet; B¹ is the electro-
magnet of the repeating instrument; C' is an iron lever pivotted at o, and counter-
balanced by a spring at d adjustable so as to regulate the pressure on the carbon
g. The primary circuit of the induction coil I' passes through the plates f, h, and
the carbon g. When a pulse from the distant station modifies the power of the
magnet B¹, the pressure varies, the resistance of the local circuit and of the coil I
is changed, and a current is induced in the secondary coil of I' and line P of a
direction and force corresponding with that transmitted. This arrangement neces
sitates a double establishment between the stations. A more delicate transmitter
is shewn at Fig. 2, Sheet II. B' is the electro-magnet; A', the polarised magnet;
c, the diaphragm, with a contact or carbon at x. Fig. 3, Sheet II., shews diagram-
A is the carbon
matically a complete arrangement connecting two stations.
transmitting instrument placed in the primary circuit of the induction coil D,
and B is the receiving instrument; C, a commutating key by which the trans-
mitter can be put in circuit with the battery K, and coil D, or the apparatus
can be put in circuit for a call signal by moving the key C several times against the
contact a, so that a powerful secondary current thus sent into line actuates the
polarised tongues of the relays F bringing into action the local circuits for
the call bells H which are worked from the same batteries K as those used for
the telephones.
Having thus described the nature of the said Invention, and in what manner the
same is to be performed as communicated to me by my foreign correspondent, I
claim in respect of telephones and their connections,―
First. Mounting the carbon of a transmitter on an adjustable spring, so that the
pressure may be regulated without bruising the carbon.
Second. The combination of the casing and its cover and mouth piece, the
diaphragm adjusting spring and carbon fixed thereon.
Third. The combination of two plates or diaphragms p and k with finely divided
carbon or analogous substance interposed to constitute the regulator and the
circuit connections for these.
Fourth. The combination with the diaphragm of two or more contacts thereon,
and their circuit connections whereby the line current is made to undergo varia-
tions corresponding in intensity with the force of the pulses acting on the
diaphragm.
Fifth. The combination of the diaphragm and resonant tube with an electro-
magnet having an armature in form of a blade spring held at its ends, as herein
described with reference to Figs. 7, 8, and 9 on Sheet I of the accompanying
Drawings.
Sixth. The combination of two electroids immersed in separate compartments
containing conducting fluid, communicating through a small passage the area of
which is varied by sonorous vibrations, the electrical resistance being thereby
varied.
Seventh. In combination with a telephonic circuit and the primary circuit of an
induction coil, the carbon contact us herein described.
Eighth. The arrangement and combination of the case, mouthpiece, pipe, and
vibrating diaphragm as herein described with reference to Fig. 10, Sheet I.
Ninth. The combination of the diaphragm and its support, the spring, the weight
or disc, the contact parts, and the regulating screw, as herein described with
reference to Figs. 1 to 5, Sheet I., inclusive.
Tenth The construction of the diaphragmn of metal discs held together with soft
paper or other similar material interposed between them.
Eleventh. The construction of transmitter herein described with reference to
Fig. 2, Sheet II,
Twelfth. The construction of the transmitter A furnished with several thin
metal plates roughed off in (combination with the diaphragm and electric circuit
passing through the said plates.

page_text: Thirteenth. The combination of the transmitter A, the induction coil D, the
commutator C, the polarised relays F, the call bell H, the batteries K, and circuits
arranged and operating as herein described with reference to Fig. 3, Sheet II.
In witness whereof, I, the said John Imray, have hereunto set my hand and
seal, this Sixteenth day of December, in the year of our Lord One thousand
eight hundred and seventy nine.
JOHN IMRAY. (L.S.)