Improvements in Telephonic Apparatus.
Year: 1895

page_text: Date of Application, 18th Jan., 1895
Complete Specification Left, 8th Oct., 1895-Accepted, 18th Jan., 1896
Improvements in Telephonic Apparatus.
I, WILLIAM EDWARD LANGDON, Electrical Engineer, Midland Railway,
Derby, do hereby declare the nature of this invention to be as follows:-
In an improved form of telephonic transmitter by which articulate speech is
transmitted with great clearness and in the employment of which all crevices
or recesses by which dust or other undesirable products may accumulate are
avoided.
To this end I superimpose upon the existing diaphragm another diaphragm
composed of metal wood or other material sufficiently elastic for the purpose in
such a manner that it shall enclose an air space or have between it and the face of
the ordinary or electrical diaphragm an enclosed space.
On speaking to or in the neighbourhood of the outer or superimposed diaphragm
pressure is by the vibration imparted to it conveyed by the enclosed air to the
inner or electrical diaphragm causing it to transmit electrical or electro-magnetic
currents in the ordinary manner. The volume of air in the enclosed space acts
upon the inner diaphragm with great harmony rendering the communication full
and clear; and the outer diaphragm being merely a sheet of wood, metal, &c.,
is free from all interstices recesses &c. and is readily wiped clean at any
moment.
Dated this 17th day of January 1895.
I, WILLIAM EDWARD LANGDON, Electrical Engineer, Midland Railway,
Derby, 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 consists in an improved form of telephone transmitter by which
articulate speech and other sounds are transmitted with great clearness and in the
employment of which crevices or recesses in which dust or other undesirable
matters may accumulate are avoided.
To this end I superimpose upon the ordinary existing electrical diaphragmi
another diaphragm of metal, wood or other suitable material sufficiently elastic for
the purpose in such manner that it shall enclose an air space, or have between it
and the face of the ordinary diaphragm an enclosed air space.
Fig. 1 of the accompanying drawings shows as an example a half front elevation
and Fig. 2 a vertical section through an ordinary telephone transmitter with my
improvements applied thereto.
A is the ordinary electrical diaphragm and B the diaphragm placed in front of
it according to my invention; this diaphragm B is fixed upon the wooden casing D
by a metal frame E and countersunk screws, it may be of wood in the form of thin
veneer. As an example in the form here shewn the diaphragm may be of well

page_text: "
seasoned pinewood veneer about 044 of an inch thick, with polished surface so that
it can be wiped clean and dry as required. If the diaphragm B is made of "tin
I have found a thickness of about 009 of an inch suitable. But I may employ
any other suitable sheet material sufficiently resilient, or elastic in its action to
respond to the varying pressures brought to bear upon it by the voice of the
speaker.
Between the diaphragms A and B is an enclosed air-space C, a layer of thin
blotting paper or other suitable material being inserted around the edges of the
diaphragm B between the latter and the frame D in order to afford free action
10 B to enable it to respond to the air waves which impinge upon it when it is
spoken to.
Fig. 3 is a front view and Fig. 4 a vertical section of another example or form
which has also been found perfectly suitable to the purpose.
A is the electrical diaphragm and B the outer or mechanical diaphragm, which
is held in place by the ring frame E. C is the air space between the two
diaphragms.
The
On speaking to or in the neighbourhood of the outer or superimposed
diaphragm B pressure is by the undulatory vibrations imparted to it, conveyed by
the air enclosed in the space C to the inner or electrical diaphragm A, causing it
to transmit electrical or electromagnetical currents in the ordinary manner.
volume of air in the enclosed space C acts upon the inner diaphragm with great
harmony rendering the communication full and clear, and the outer diaphragm B
being a sheet of wood, metal or other suitable material free from interstices,
recesses or other parts wherein dust or other matters could accumulate is if
necessary readily wiped clean at any moment.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The application and use in telephone transmitters of an outer resilient
diaphragm and an enclosed air space between it and the electrical diaphragm for
the purpose stated.
2. The improved forms of telephone transmitter having an outer resilient
diaphragm B and an enclosed air space C between it and the electrical diaphragm
as shewn on the drawing.
Dated this 8th day of October 1805
JENSEN & SON,
77 Chancery Lane, London, W.C., Patent Agents.