An Improvement in or connected with Mechanical Telephones.
Year: 1891

page_text: Date of Application, 23rd Feb., 1891
Complete Specification Left, 21st Nov., 1891-Accepted, 24th Dec., 1891
PROVISIONAL SPECIFICATION.
An Improvement in or connected with Mechanical Telephones.
I, FORREST WILLIAM DUNLAP of 57 Rupert Street, Piccadilly, London, W.
Engineer, do hereby declare the nature of this invention to be as follows:-
My invention relates to an exchange system for mechanical telephones, and has
for its object to enable instruments connected to different lines to be put into direct
communication with each other so that conversation may be carried on through
the two lines.
The invention consists of an acoustic coupling tube adapted to be attached to the
mouthpieces of any two terminal instruments arranged in suitable proximity to one
another at the central office or exchange, whereby the vibrations of the diaphragm
of the one instrument will be transmitted through the column of air contained in
the tube and so directly communicated to that of the other instrument.
30 13
CL
1901
F. W. DUNLAP.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.
COMPLETE SPECIFICATION.
An Improvement in or connected with Mechanical Telephones.
I, FORREST WILLIAM DUNLAP, of 57, Rupert Strect, Piccadilly, London, W.,
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 an exchange system for mechanical telephones, and has
for its object to enable the terminal instruments of different lines to be put into
direct through communication with each other so that conversation may be carried
on through the two lines.
The invention consists in the combination of an acoustic coupling tube with any
two terminal instruments arranged in suitable proximity to one another at the
central office or exchange, whereby the vibrations of the diaphragm of the one
instrument, will be transmitted through the column of air contained in the tube and
so directly communicated to that of the other instrument.
The invention is illustrated in the accompanying drawings, forming part of this
Specification, wherein I have represented a plan shewing the connection of the ends
of the coupling tube with the two instruments in section.
The coupling tube a is a length of air-tight flexible tubing strengthened by an
internal wire coil, as used for speaking-tube purposes, and it terminates in metal
tubular end pieces 6 adapted to fit tightly into sockets c fixed in hinged doors d
covering the mouthpieces of the terminal instruments, which are provided with
diaphragins and are of the usual construction in mechanical telephones.
For coupling up, the doors d, which are normally open for ordinary use of the
instrument, are closed and the ends of the tube a inserted in the sockets c, as shewn,
the sockets c then projecting into, and virtually forming continuations of, the
mouth-pieces e.
Instead, however, of the doors and sockets, the ends of the coupling tube might
fit directly into the mouth-pieces e, if preferred.

page_text: 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. The combination, with two mechanical telephones, of an acoustic coupling
tube adapted to connect the mouth-piece apertures of two adjacent instruments for
the purpose of putting the two telephonic lines into through communication, as
specified.
2. The combination, with two mechanical telephones, of hinged doors.carrying
sockets adapted to form continuations of the mouth-pieces of the instruments and of
an acoustic coupling tube adapted to fit in and connect such sockets and mouth-
pieces, substantially as specified.
Dated this 21st day of Narambon 1981
F. W. DUNLAP.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.