IMPROVEMENTS IN TELEPHONIC TRANSMITTING INSTRUMENTS
Year: 1885

page_text: We, SILVANUS PHILLIPS THOMPSON, of University College, Bristol, Doctor of
Science and Professor of Experimental Physics, and PHILIP JOLIN, of 2 Elmdale
Road, Redland, Bristol, Engineer do hereby declare the nature of our invention
for "IMPROVEMENTS IN TELEPHONIC TRANSMITTING INSTRUMENTS and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
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In the complete specification left at the Patent Office in connection with our
application for a patent for "Telephonic transmitting instruments or valve
telephones" N° 8524 of the year 1884, we set forth fully the advantages which
result from the use of a free piece, (which we therein termed and hereinafter terin
a valve,) in place of a diaphragm, tympanum, reed, tongue or other vibrator fixed
at one or more points, in order to take up the motion of the sound-waves and
produce the variations of an electric current requisite to transmit the sounds in the
well-known manner.
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And the invention described in our said former specification relates chiefly to
arrangements wherein the said free piece or valve is used as one of the contact-
pieces of a current-regulator, and the other contact-piece of the current-regulator
forms a seat for the valve.
We have found, however, that many of the advantages which the valve form of
construction possesses over existing instruments may be obtained by arrangements
of the valve telephone in which the valve and valve-seat do not necessarily form
the contact-pieces of the current regulator, and in which some other features of our
former invention are varied.
Our present invention relates to telephonic transmitters such as are hereinbefore
referred to, in which, instead of a diaphragm, tympanum, reed, tongue or other like
vibrating piece fixed at one or more points, we use a piece which we term a valve,
which is free to move, as a whole, under the influence of the sound-waves, without
deformation or change of shape.
Figure 1 shows such an arrangement, in which a is the valve made of suitable
conducting material and preferably of a spherical form, resting upon or over a
tubular cavity d in the block B, through which the sound-waves are suitably
directed upwards upon the valve a. i, i are two or more loose contact-pieces,
supported by the valve a and by the posts k, k, as shown, all of suitable conducting
material. The posts k, k form the electrodes, and the current passes to the external

page_text: circuit through the posts, contact-pieces and valve. Under the influence of the
sound-waves, the valve is lifted to an infinitesimal extent from its seat and the
variations of the contact-points thereby caused, produce the variations of the
electric current requisite for the reproduction of the sound-waves.
In the arrangement above described, it is not necessary that the valve should
entirely close the orifice, round which small apertures may be left, if desired. Also,
the valve may be supported above the orifice by a light spring, in any manner
which will leave it free to move under the impulse of the sound-waves. Also, the
sound-waves may be directed upon the valve in any convenient manner, and in
any direction which will cause the requisite motion of the valve. We prefer to
direct the sound-waves from below upwards as shown, by means of a speaking-tube
and mouth-piece. Furthermore the contact-pieces may take the form of light
springs as shown in Figure 2.
Figure 2 shows an arrangement of a similar character in which the valve a takes
the form of a piston, of somewhat smaller size than the orifice of the tube d, and
supported by a light spring m, which may be regulated to give the requisite
pressure between the valve a and the spring contact-pieces i, i, which may be of
platinum or platinum-tipped. With this arrangement, the sound-waves may be
advantageously directed upon the valve from above.
It is not necessary, in order to secure the advantages of our arrangement, that
the valve itself should be of conducting material. For instance, in either of the
above described arrangements, the valve might be of wood, rigidly connected with
a contact-piece of a shape suitable to take the place of the portion of the valve
which is in contact with the pieces i, i above.
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In such cases, the valve, moving as a whole, will suitably actuate or influencé
the contact-pieces. Figure 3 illustrates an arrangement of this kind. The valve a,
which may be of wood or other non-conductor, carries a contact-piece a² on the
upper extension of a stalk, the lower extension of which may be provided with
a counterpoise. This contact-piece a² of suitable material bears upon two other
contact-pieces c¹, c³ by means of prominences or pins a³. The contact pieces c¹, c³,
'which serve as electrodes, may be springs, and these springs, and the pins a³, may
be platinum or platinum-tipped. The valve may be suspended over the orifice by
a light spring, if desired, and may be of any suitable shape.
The contact-pieces of the arrangements above described may be of any material
which gives good results in current-regulators or microphones as at present used.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is
The arrangements of telephonic transmitters herein before described.