Improvements in Mechanical Telephones.
Year: 1889

page_text: Date of Application, 12th Oct., 1889
Complete Specification Left. 14th July. 1890-Accepted. 27th Sept., 1890
PROVISIONAL SPECIFICATION.
Improvements in Mechanical Telephones.
I, FOREST WILLIAM DUNLAP of 26, Coventry Street, in the County of Middlesex,
Engineer, do hereby declare the nature of this invention to be as follows:-
My invention relates to mechanical telephones; and has for its object to enable a
single transmitting and receiving instrument to be readily connected up in operative
position with any one of a series of different wires or circuits instead of using as
many pairs of instruments as there are wires as hitherto.
The invention consists in making the instrument movable upon guides in such
manner that a hook or equivalent fastening attached to the diaphragm of the
instrument may be readily connected to any one of a series of eyes forming the
terminals of the several wires, the guides being bodily movable away from the said
terminals so as when the diaphragm hook has been engaged in the terminal of one of
the wires to raise the said terminal off its seat and transfer the strain of the wire to
the diaphragm which is necessary for the transmission of vibrations between them.
The instrument is supported upon its guides by stirrup pieces free to slide along
and across the guides in such a way as to permit the easy engagement of the
diaphragm hook with any one of the terminals. The guides are carried by brackets
fitted to slide in the direction of the strain of the wires and the brackets are jointed
to, and operated by, a lever frame worked by a pressure screw or otherwise, for the
purpose of varying the distance of the guides from the terminals.
Date This 12 day of October 1003.
F. W. DUNLAP.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.
COMPLETE SPECIFICATION.
Improvements in Mechanical Telephones.
I, FOREST WILLIAM DUNLAP of 26, Coventry Street in the County of Middlesex,
Engineer, 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 mechanical telephones.
Heretofore the transmitting and receiving instruments have been permanently
connected with their respective line wires, there being therefore as many instruments
as there are lines terminating in one place, and my invention has for its object to
enable one instrument to be readily coupled up for operation in connection with any
one of a number of such line wires.
Reference is to be had to the accompanying drawings, forming part of this
specification, wherein
•
Figure 1 is a front elevation of the instrument
Figure 2 a central vertical cross-section and
Figure 3 a horizontal section thereof on line 1. 1, Figure 2.
The same reference letters indicate the same parts in all the figures.
The operative parts of the instrument are mounted in and on a suitable box like
base A fixed against the wall or other support. B is the transmitting and receiving
instrument of the ordinary construction, comprising a diaphragm fixed in a box
provided with a mouth piece there being permanently connected to the diaphragm a
rod or wire b. projecting rearwardly through the back of the diaphragm box and

page_text: terminating in a hook b¹ or equivalent means of connection with the terminals of the
line wires, of which one is shewn at Cin Figure 2. The several wires C lead through
a row of holes a in the base plate A, and their respective terminals are loops or
eyes c, c, c, etc., attached to shanks of disc like heads c' and arranged in a row, as
shewn in Figure 1. The heads c¹ are seated, when the line wire is not coupled up,
against a loose strip of leather x covering the holes in the base plate A and through
small holes in which the line wires pass, the object being to prevent contact of the
line wire with the wooden base.
The instrument is movable upon a pair of guide bars D parallel to each other and
situated in front of, and parallel to, the row of terminals ccc etc., the instrument
being movable both in the direction of the length of the guide bars, and also, to a
limited extent, in the direction of its own axis to enable the hook 6' to be moved along
in front of the row of terminals ccc etc. and to be readily connected with any one of
them, as required, the guide bars D) being movable away from the said terminals so
as, when the diaphragm hook 6¹ has been so connected with one of the terminals, the
latter will be raised off its seat x and the strain of the line wire will be transferred to
the diaphragm, which is necessary for the transmission of vibrations between them.
For this purpose, the instrument B is supported upon its guides by stirrup pieces E
embracing the guide bars D and free to slide along the same, the stirrup pieces being
of greater depth than the depth of the bars D so as to permit limited independent
motion of the instrument in the direction of the wires C when the guide bars
are in their rearmost position (as shewn in dotted lines in Figure 2). The guide
bars D are carried by posts on brackets F whose stems fare fitted to slide through
the base A in the direction of the strain of the wires C and the brackets F are
jointed to, and operated by, a lever frame composed of two side members GG
pivoted at g and a cross-member G₁ said frame being worked by a pressure screw H
or otherwise.
In order to uncouple the instrument B, the screw H is turned and the lever
frame G and instrument brought to the dotted position, Figures 1 and 2, by the
strain of the line wire with which the instrument is connected. The hook b¹ can then
be detached and by drawing forward the instrument on its guides D it may be slid
freely along in front of the terminals and hooked into any one of them. By then
moving the screw and lever frame to the full line position the guides and instrument
are moved forward thus raising the terminal in which the hook has been inserted off
its seat and bringing the full strain of the line wire on the diaphragm of the
instrument.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is;
1. In a mechanical telephone, the combination, with two or more line wire
terminals, of a transmitting and receiving instrument provided with means of
connecting its diaphragm with any one of said terminals, and of applying the strain
of the line wire to said diaphragin, substantially as and for the purpose, specified.
2. In a mechanical telephone, the combination, with two or more line. wire
terminals arranged in a row and temporarily supported as described, of a trans-
mitting and receiving instrument provided with means of connection therewith and
of parallel guide bars movable towards, and away from, the terminals and upon
which the instrument is movable, as described.
3. In a mechanical telephone, the combination, with two or more line wire
terminals arranged in a row and temporarily supported as described, of a trans-
mitting and receiving instrument provided with means of connection therewith,
parallel guide bars movable towards, and away from, the terminals and upon which
the instrument is movable as described, and of a lever frame and pressure screw for
operating the guide bars and transferring the strain of the line wire to the diaphragm
of the instrument, as specified.

page_text: 4. The combination, with the respective line wires, of terminals adapted to engage
with the diaphragm of the transmitting and receiving instrument and to support the
strain of the line wire when not coupled up, as described.
F. W. DUNLAP.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.