Year: 1886

page_text: I, WILLIAM MCPHERSON of St. Stephen's Chambers, Telegraph Street, in the
City of London, Electrician do hereby declare the nature of this invention to be
as follows:
My invention relates to telephones of the kind in which two tympans or
diaphragms capable of vibration are connected by a stretched wire or cord, so
that speech or other sounds, emitted in the presence of one of these diaphragins,
is transmitted to the other, by which it is reproduced. The chief object which
I have in view is to be enabled to put the connecting wire or cord under very
considerable tension, without imposing undue strain ou the diaphragms, as I find
that I can thus make the apparatus more effective over considerable distances.
For this purpose, at each of the two connected instruments, I pass a loop of the
connecting wire or cord through the centre of the diaphragm and fix it to a
washer or plate in front thereof. Centrally behind the diaphragm and bearing
against it I place a small ring, and from this ring I pass several wires through
holes in the diaphragm and in the washer in front of it, and I carry these wires
radially from the washer over pullies, rollers or guides supported by the framing
preferably on tense cross wires. From these pullies, rollers or guides the wires
pass backwards again through holes in the diaphragm about midway between its
centre and its circumference to a ring, to which they are attached, this ring is
supported at some distance behind the diaphragm by struts extending from it to
a ring which bears against the back of the diaphragm where the wires pass through
it. Thus the tensile strain of the connecting wire or cord tending to bulge the
central part of the diaphragm backwards is to a great extent moderated by the
tension of the radiating wires which deliver through the ring to which they are
attached and the struts and ring supporting it, a strain tending to bulge the
diaphragm forwards. On the ring which is strutted back from the diaphragm
may be mounted a pulley, roller or guide by which the connecting rod or cord
may be led away at an angle. When this is not necessary, in cases where the
wire or cord passes perpendicularly away from the diaphragm, the struts and the
ring which they support may be dispensed with, the radiating wires being simply
Di31

page_text: attached to the ring that bears against the hinder surface of the diaphragm where
the wires pass through it about midway between the centre and the circumference.
When the connecting wire or cord has to turn a corner in its course from the
one instrument to the other, I pass it over a small guide pulley free to revolve
upon a tense wire which is capable of vibrating.
At each instrument I prefer to provide a damper pad which can be kept pressed
against the connecting wire or cord when it is desired to muffle the sound preventing
transmission of articulation, but not preventing the transmission of sound sufficient
to operate as a signal, such sound being, if desired, produced by a gong or bell
connected to the instrument. When it is desired to employ an electrical bell or
gong for signalling, the connecting wire may be used as a conductor.
Dated this 1st day of January 1886."

page_text: A Construction of Mechanical Telephones.
I, WILLIAM MCPHERSON of St. Stephens Chambers, Telegraph Street in the
City 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:-
My invention relates to telephones of the kind in which two tympans or
diaphragms capable of vibration are connected by a stretched wire or cord so that
speech or other sound, emitted in the presence of one of these diaphragms, is
transmitted to the other, by which it is reproduced. The chief object which
I have in view is to be enabled to put the connecting wire or cord under very
considerable tension without imposing undue strain on the diaphragms, as I find
that I can thus make the apparatus more effective over considerable distances.
For this purpose, I construct each of the diaphragms and attach to it the connecting
wire or cord as I will describe referring to the accompanying drawings. Fig. 1 is
a section through the diaphragm and the front part of the casing in which it is
held. Fig. 2 is a front view of the diaphragm, the front cover being supposed to
be removed, and Fig. 3 is a view of part of the back of the diaphragm. D is the
diaphragm which may be of thin wood or other resonant material held in a casing C
between caoutchouc or other soft rings c. In the centre of the diaphragm, close to
its front side, is a plate of metal P, and behind it is a small ring A.
At some
distance behind the diaphragm is a metal ring B which is supported by four struts S
connecting it to a ring E resting by four props F against the diaphragm. At a
little distance in front of the diaphragm there are four small rollers R free to
revolve on wires G that can be tightened like those of a piano by turning pins K.
Four wires Tare attached to the hinder ring A, pass through holes in the diaphragm
and in the front plate P pass over the rollers R through holes in the ring E and
are attached to the ring B. By turning the pins K so as to strain and tighten the
wires G carrying the rollers R, the wires T are tightened radially from the centre
of the diaphragm, while the strain is conveyed through the ring B and its struts S
and props F to the back of the diaphragm. Now the connecting wire W which
passes through the centre of the diaphragm and of the plate P and is held by
a cross pin L can be put under great tension without injuriously straining the
diaphragm, for the strain transmitted through the wires T to the ring B and
thence to the back of the diaphragm tends to press it forwards while the tension
of the wire W tends to draw it backwards the two forces being therefore nearly
equilibrated.
Obviously, instead of the four wires T and struts S, there might be three or a
number greater than four. The wire W has sometimes in its course from the one
diaphragm to the other to turn round corners. In such cases it may pass partly
round a roller supported like the roller R on a wire that can be tightened like the
wire G.
In cases where the wire has to pass away from the instrument at an angle, I pass
the wire W over a pulley M and strain it by a weight, and to any part of W within
the pulley I attach the communicating wire W' as indicated by the dotted lines in
1

page_text: By arranging the diaphragin D as above described with means of equilibrating
the strain of the connecting wire W, a very thin diaphragm may be employed in
conjunction with a very tight wire, and thus great loudness and distinctness can
be obtained in the sounds transmitted.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is
For equilibrating strain on the diaphragın of a mechanical telephone, in com-
bination with the diaphragm D and the connecting wire W the ring A connected
by wires T that are adjustable in tension to the ring B supported against the
diaphragm substantially as described.