AN IMPROVED TELEPHONIC TRANSMITTER
Year: 1885

page_text: I, CHARLES DENTON ABEL, of N° 28 Southampton Buildings, Chancery Lane in
the County of Middlesex, Consulting Engineer and Patent Agent, do hereby
declare the nature of my invention for "AN IMPROVED TELEPHONIC TRANSMITTER
to be as follows:-
•
»
This invention relates to an improved construction of telephonic transmitter in
which there are provided double contacts and conducting wires whereby a greater
intensity of the sound transmitted is obtained than with apparatus of present con-
struction. For this purpose, the diaphragm carries two separate contact pieces of
carbon or other suitable semi conductor, insulated from each other and situated a
slight distance apart, between which enters a third contact piece of a wedge shape
supported by a horizontal arm projecting from a cylindrical mass that is suspended
loosely from a rod of conducting material, so that the wedge shaped contact piece
tends by its own weight and that of its arm to enter between and come in close
contact with the two diaphragm contacts, the cylindrical body being however
provided on the side opposite to the said arm with an adjustable counterweight for
regulating the degree of pressure of the wedge contact upon the others. From
each of the diaphragm contacts a conducting wire passes to the opposite ends of a
bobbin on which they are both coiled to the same hand, but run along the same in
opposite directions; after leaving the bobbin the two wires are joined to a single
one leading to the one pole of a battery, the other pole of which is connected to
the suspension rod of the cylindrical body. The bobbin is also provided with the
usual induction coil leading to the receiving instrument. When the instrument is
not in action, the current from the battery passes equally through the coils of the
two diaphragm contacts, and the effect of these upon the core being thus neutralized,
no induction takes place. On the instrument being put in action, the vibrations of
the diaphragm alternately cause the pressure of one of its contacts against the
wedge contact to increase and that of the other to decrease, whereby the current

page_text: passing through the coil of the first named contact will be increased and that of
the other will be decreased, and the core being thus polarized in a corresponding
manner, corresponding currents will be induced in the coil of the receiver. Thus
a double current will be transmitted for each complete vibration of the diaphragm,
and this combined with the energetic action of the wedge contact will give results
superior to any hitherto obtained.
Instead of making all three contacts of semi-conducting material, the one or
other set may be of perfect conducting material.
The diaphragm may be provided with two or more sets of such contacts, which
may either all be connected to the same bobbin or to different bobbins, in which
case their wires may be connected up either in tension or in quantity; also, there
may be either only one battery common to all the bobbins or a separate one to each,
so that if each set of contacts has a separate bobbin and a separate battery, the
apparatus will constitute as many separate transmitters.
Again, instead of a single bobbin with two coils, there may be used two bobbins
each with a single coil, by connecting each to parallel contacts, and directing the
currents in the required manner. Also, only a single contact and bobbin may be
utilized.
This apparatus may also be worked by transmitting battery currents direct. By
sending into the line wire one of the diaphragm contact currents, the other current
will pass to earth after passing through a suitable resistance; or one of the contacts
may be suppressed; or if the line has two wires, the currents from the two contacts
may each be sent respectively into one of the wires.
Instead of suspending the cylindrical mass, it may be carried in fixed guides or
on rollers &c so long as it is free to move in a horizontal direction. Also, the two
contacts may be carried by the cylindrical body, and the wedge contact by the
diaphragm. The pressure of the wedge contact may be effected by other means,
such as springs, regulating screws &c, instead of or in addition to its weight.
Dated this 28th dex of August 1885

page_text: I, CHARLES DENTON ABEL of N° 28 Southampton Buildings, Chancery Lane in
the County of Middlesex, Consulting Engineer and Patent Agent 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:-
This invention relates to an improved construction of telephonic transmitter in
which there are provided double contacts and conducting wires whereby a greater
intensity of the sound transmitted is obtained than with apparatus of present
construction.
Fig. 1 of the accompanying drawings shews a diagram of the principal parts of
this apparatus.
The diaphragm V carries two separate contact pieces C C¹ of carbon or other
semiconductor, insulated from each other and secured a slight distance apart upon
a support ; between these enters a third contact piece T also of carbon, or other
semiconductor of a wedge shape, supported by a horizontal arm projecting from
a cylindrical mass M that is suspended loosely at its centre from a rod or fork E
of conducting material, so that the wedge shaped contact piece tends by its own
weight and that of its arm to enter between and come in close contact with the
two diaphragm contacts C C¹ the cylindrical metallic body M being however
provided on the side opposite to the said arm with an adjustable counterweight P
for regulating the degree of pressure of the wedge contact T upon the others.
From each of the diaphragm contacts CC' a conducting wire F F¹ of equal length
passes to the opposite ends of the bobbin I on which they are both coiled to the
same hand, but run along the same in opposite directions; after leaving the bobbin
the two wires are joined to a single one at O leading to the one pole of a battery,
the other pole of which is connected to the suspension rod of the cylindrical
body M and through this with the contact T. The bobbin is also provided with
the usual induction coil leading to the receiving instrument. When the instrument
is not in action, the current from the battery passes equally through the coils of
the two diaphragm contacts, and the effects of these upon the core being thus
neutralized, no induction takes place. On the instrument being put in action, the
vibrations of the diaphragm V alternately cause the pressure of one of its contacts
against the wedge contact to increase and that of the other to decrease, whereby
the current passing through the coil of the first named contact will be increased
and that of the other will be decreased, and the core being thus polarized in
a corresponding manner, corresponding currents will be induced in the coil of
the receiver. Thus a double current will be transmitted for each complete
vibration of the diaphragm, and this combined with the energetic action of the
wedge contact due to the inertia of the mass M, which is opposed to the vibrations

page_text: of V, will give results superior to any hitherto obtained. The pressure of the
contact T upon C C¹ can be regulated by adjusting the counterweight P. Instead
of making all three contacts of semiconducting material, the one or other set may
be of perfect conducting material such as platinum.
The diaphragm may be provided with two or more sets of such contacts, which
may either all be connected to the same bobbin or to different bobbins, in which
case their wires may be connected up either in tension or in quantity, as may be
required; also, there may be either only one battery common to all the bobbins
or a separate one to each; so that if each set of contacts has a separate bobbin and
a separate battery, the apparatus will constitute as many separate transmitters.
Again, instead of a single bobbin with two primary coils, there may be used
two bobbins each with a single coil, by connecting each to parallel contacts, and
directing the currents in the required manner. Also, only a single contact and
bobbin may be utilised.
This apparatus may also be worked by transmitting battery currents direct.
By sending into the line wire one of the currents, passing through C or C, the
other curient will pass to earth after passing through a suitable resistance pro-
portionate to that of the line; or one of the contacts may be suppressed; or
if the line has two wires, the currents from the two contacts may each be sent
respectively into one of the wires.
Instead of suspending the cylindrical mass M it may be carried in fixed guides
or on rollers or on pivotted supports &c so long as it is free to move in a horizontal
direction. Also, the two contacts C C¹ may be carried by the cylindrical body M,
and the wedge contact T by the diaphragm. The pressure of the wedge contact
may be effected by other means, such as springs, regulating screws &c instead of or
in addition to its weight.
Figa 2 and 3 shew vertical sections and Fig. 4 a horizontal section of the above
described apparatus as actually constructed. The diaphragm V is fixed to the
mouthpiece B by means of a caoutchouc stud a cemented to the diaphragm and
mouthpiece. To the diaphragm is fixed the insulating support a carrying the two
contacts C, C¹ of carbon or other material, between which rests the wedge contact T
carried by the metal body M, supported by the branches of the metal fork E by
means of which the current is conveyed to the wedge T.
The current entering through the wire A passes through the contacts G G¹ and
commutator H to a metal plate J to which is pivotted the fork E
Each of the contacts C C¹ is connected by a wire K K¹ to one of the ends of the
primary coils F F1 of the bobbin I, the other ends of which are united to a single
wire at O on leaving the bobbin, which wire passes to the other pole of the
battery.
The induced current passes into the line through the wires P¹ pu and thence to
the receiver.
The other parts of the transmitter, such as the commutator &c do not differ
from those usually employed. If in place of keeping the contact T in position by
weight only, it be held by springs or setting screws, the diaphragm might be placed
in a horizontal or inclined position, as shewn at Fig. 5, where the wedge contact T
is held by two springs R R¹ pressing in the direction of the arrow against the
action of the screw X, which serves to adjust the pressure of T.
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 in respect of telephonic transmitters is :-
1. The use in combination with the diaphragm, of two contacts attached thereto
each of which is connected to a separate conducting wire, and a wedge contact
interposed between these and so arranged as to oppose by inertia the vibrations*
imparted to the other two contacts by the diaphragin substantially as and for the
purposes herein described.

page_text: 2. Connecting the wedge contact referred to in the preceding claim to a suspended
mass or to springs or equivalent devices for affording it the requisite inertia,
substantially as herein described.
3. Connecting the wires of the two diaphragm contacts referred to in the first
claim, each to one end of two primary coils of an induction apparatus the other
ends of which coils are connected to a single wire leading to the one pole of the
battery, whose other pole is connected to the wedge contact, so that the induced
current sent into the line is produced in the secondary coil by the differential
action of the two currents in the primary coils resulting from the combined action
of the two diaphragm contacts and the wedge contact.
ABEL & IMRAY,
Agents for the Applicant.