IMPROVE- MENTS IN ELECTRO-TELEPHONIC TRANSMITTERS
Year: 1885

page_text: I ALAN ARCHIBALD CAMPBELL SWINTON of 43 Grove Street Newcastle upon
Tyne Engineer do hereby declare the nature of my said Invention for "IMPROVE-
MENTS IN ELECTRO-TELEPHONIC TRANSMITTERS" to be as follows:-
My Invention relates to improvements in electro telephonic transmitters by
means of which sounds are electrically transmitted to a distance by causing the
atmospheric sonorous vibrations to act directly upon a moveable contact piece or
pieces vibrating in unison with the said sounds and controlling electric currents.
flowing through the apparatus no diaphragm or tympanum being employed to
collect the said sonorous vibrations which act directly on the before mentioned
contact pieces.
In instruments as hitherto constructed upon this principle the true vibrations of
the contact pieces is interfered with by secondary vibrations produced by the action
of the atmospheric sonorous vibrations upon the case of the instrument or the
supports of the microphone or the walls of the apartment to which the instrument
is fixed their secondary vibrations being communicated to the fixed contact pieces
of the microphone and causing the transmitted sounds to be defective and
indistinct.
According to my Invention to obviate these defects I so connect the microphone
proper, upon which the sound waves act, to the case or support of the instrument
that vibrations communicated to the latter do not in any way affect the said
microphone proper which is therefore only acted upon by the direct atmospheric
sonorous vibrations. I may effect this by mounting the microphone proper in a
massive or ponderous frame or support of lead or other equivalent material of great
inertia and high specific gravity and in some cases I suspend the said frame or
support by means of springs or bands of India rubber or other elastic substance or
I mount it upon layers or washers of felt or other suitable non-sonorous material.
The method of suspension by an elastic medium may be used without the before
described heavy frame. By this arrangement the above mentioned defects due to
secondary vibrations as aforesaid are obviated for the inertia of the heavy frame or
the method of support or both prevents or prevent the microphone from being
affected by the said secondary vibrations and as the sound waves act only on the

page_text: microphone proper as regards the moveable contact or contacts the articulation is
much improved. In some cases in order to direct the sound waves onto the
moveable contact or contacts I employ a speaking tube or mouthpiece which is
however attached to the case of the instrument in such a way that the vibrations
of the tube or mouthpiece are not communicated to the microphone proper. The
microphone proper may be of any convenient description but I prefer that described
in the Specification of my application for Patent No 16954 of 1884. I find it
advantageous in some cases to use for the contact pieces of the transmitter carbons
of low specific gravity and high conductivity which may be obtained by the
carbonization of organic material in a closed retort and the subsequent treatment
of the product with carbonaceous material and recarbonization this process being
repeated as often as necessary...

page_text: I ALAN ARCHIBALD CAMPBELL SWINTON of 43 Grove Street Newcastle upon
Tyne 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 improvements in electro telephonic transmitters by
means of which sounds are electrically transmitted to a distance by causing the
atmospheric sonorous vibrations to act directly upon a moveable contact piece or
pieces vibrating in unison with the said sounds and forming microphonic contact
with another contact piece or several such pieces thus controlling electric currents
flowing through the apparatus no diaphragmn tympanum or auxiliary sound
receiving surface being employed to collect the said sonorous vibrations and
communicate them mechanically to the microphone which is as before mentioned
actuated solely by the direct action of the atmospheric sonorous vibrations upon
itself alone.
In instruments hitherto constructed on this principle the true vibration of the
microphonic contact pieces is very liable to be interfered with by secondary tremors
or vibrations produced by the action of the atmospheric sonorous vibrations and
other causes upon the case of the instrument the supports of the microphone or the
walls of the apartment to which the instrument is fixed these secondary vibrations
being communicated to the microphonic contact pieces and by reason of the
extreme sensitiveness necessary for the proper working of this class of instrument
causing the transmitted sounds to be defective and indistinct and at the same time
leading to jarring and other prejudicial noises.
According to my Invention to obviate these defects I so attach the microphone
proper upon which the sound waves act to the case or support of the instrument
that vibrations of any kind communicated to the latter do not reach or in any way
affect the said microphone proper which is therefore acted upon solely by the direct
atmospheric sonorous vibrations.
I may effect this by mounting the microphone proper in a massive or ponderous
frame or support of lead or other equivalent material of great inertia and non
vibratory character the form of their support or frame being designed with a view
to its being incapable of sonorous vibration, and in some cases I mount the said
frame or support upon layers or cushions of india rubber felt or other suitable
nonsonorous material or suspend it by means of springs or by bands or pieces of
India rubber or other suitable substance.
I find that in some cases the method of suspension by springs or pieces of a
material that does not transmit sonorous vibrations is sufficient without the above
described heavy frame or support.
By these several arrangements or a combination of them the above mentioned
defects due to secondary vibrations are obviated, for the inertia and nonsonorous
character of the heavy frame or the method of suspension or support or both.
•

page_text: prevents or prevent the microphone from being affected by the said secondary
vibrations and as the sound waves act on the microphone proper only as regards
the moveable contact piece or pieces the articulation is much improved and all
jarring and burring sounds are obviated.
In some cases in order to direct the sound waves on to the microphone proper
I employ a mouthpiece which is however made of such a form and material as to
be incapable of sonorous vibration, or mounted in such a way that its vibrations
are not communicated to the microphone proper.
It is distinctly to be understood that the microphone proper may be of any
convenient description, but I much prefer that described in the specification of my
patent No 16954. of 1884.
And in order that my said Invention may be clearly understood I will now
proceed to describe means by which the same may be carried into practical effect
but I wish it to be understood that the details may be considerably varied without
departing from the nature of my invention.
In the accompanying drawings the microphone shewn is in each case of the
description contained in the specification of above mentioned patent No 16954
of 1884. and it is evident that some of the details must be varied in order to apply
my invention to microphones of other design but this will be clearly apparent from
the description herein given.
Figure 1 represents in vertical transverse section a transmitter constructed
according to my Invention, a is the microphone mounted in the massive supporting
frame b which is made of lead or other suitable non-sonorous material, and placed
on any suitable support fand I find it very advantageous to insert between such
support and frame, cushions or layers c of India-rubber, felt or other material
incapable of transmitting sonorous vibrations.
Figure 2 shews how my Invention may conveniently be applied to microphones
requiring adjustment by varying the inclination of the contact pieces to the
perpendier, b is, as before, the massive supporting frame. It is hinged at i on
to the bracket f, the inclination being readily varied by means of the adjusting
screw g. In order to prevent sonorous and other vibrations being communicated
by the bracket to the instrument frame b, the spindle of the hinge i, may
advantageously be surrounded by an India-rubber or felt tube c¹ and the point of
the screw g, may be made to bear on a cushion crecessed into the substance of
the frame b. In this figure 2, a mouthpiece d is shewn as being fitted to the
frame b of the microphone for the purpose of concentrating the sound waves on to
the contact pieces, and in order to prevent vibrations of the said mouthpiece from
being communicated to the latter, it is attached to the supporting frame 6 by means
of cushions e of a flexible springy or yielding character.
In Figure 3, the microphone and supporting frame are mounted by means of
springs, cushions or suspending and supporting pieces c of India-rubber or other
suitable material in a case f, which may be of wood but is preferably of lead or
other non-sonorous material, this case being if required screwed on to a back
board k, when it is found advantageous to insert between the case f and the back
board k, a layer of soft felt or equivalent material, in order to prevent the inside
of the case from being of a resonant nature which would be liable to cause
indistinct articulation.
In the arrangement shewn in front view in figure 4, there is no massive
supporting frame and the microphone which is held together merely by the vertical
wires or rods b is suspended by means of springs or elastic bands c in the wire
frame f, which is supported by the heavy base h.
Figures 5 and 6 represent in side and front elevation respectively a similar but
more substantial arrangement with a massive supporting frame and a device for
altering the inclination of the microphone for purposes of adjustment.
The massive supporting frame b which is of lead or other suitable material and
of a form designed with a view to its being incapable of. sonorous vibration is
-

page_text: suspended by the India-rubber pieces c between two beams f which are supported
on two pillars f¹ and f the pillar f¹ being fitted with a screw, upon which run
adjustable screwed nuts f3 between which the upper beam f is placed, by which
means the inclination of the frame b, can be readily varied.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is :-
First. In a telephonic transmitter the combination of microphonic contact pieces
(operated directly by the atmospheric sonorous vibrations without the intervention
or employment of a diaphragm or tympanum or the equivalent thereof) with a
massive and ponderous frame or support practically incapable of sonorous vibration;
in order that vibrations of the case or support of the instrument shall not be
communicated to the before mentioned contact pieces which are mounted in the
said frame or support.
Second. In combination with the subject matter of the preceding claiming
clause cushions or layers of india rubber, felt, or other material as far as possible
incapable of transmitting sonorous and other vibrations, upon or by which cushions
or layers the aforesaid massive frame or support is mounted or supported for the
purposes herein before set forth.
Third. In a telephonic transmitter having contact pieces of the description
mentioned in the preceding first claiming clause suspending the said contact pieces
by means of springs or pieces of india rubber or other suitable material either alone
or in combination with the aforesaid massive frame or support for the purposes
and substantially as hereinbefore set forth.
Fourth. In a telephonic transmitter wherein a mouthpiece is employed for the
purpose of concentrating the sonorous atmospheric vibrations upon the microphonic
contact pieces, the mounting of the said mouthpiece with cushions or layers or
springs or suspension pieces between it and the aforementioned microphonic
contact pieces in order that vibrations of the mouth piece may not be communicated
to the latter substantially as herein before described.
Fifth. The several arrangements of telephonic transmitting apparatus containing
means for preventing vibrations of the case support or mouth piece of the instru-
ment from being communicated to and interfering with the microphonic contact
pieces of the instrument substantially as herein before described with reference to
the several figures of the accompanying drawings.