IMPROVEMENTS IN SPEAKING TELEPHONE TRANSMITTERS
Year: 1886

page_text: I, WILLIAM C. TURNBULL, of Baltimore, in the State of Maryland, U.S.A.,
Merchant, do hereby declare the nature of my invention for "IMPROVEMENTS IN
SPEAKING TELEPHONE TRANSMITTERS," and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
The object of my invention is to provide a telephone transmitter having a large
capacity for transmitting electrical undulations corresponding with the waves
produced by sound, and at the same time one which will not require special
adjustment but will always remain in good working condition.
My invention relates to the general class of gravity contact telephones. I do
not broadly claim a multiple gravity contact telephone.
In the accompanying drawings
Fig. 1 is an inside view of a door of an ordinary transmitting telephone box
showing the transmitting contacts and the induction coil and circuits in diagram.
Fig. 2 is a side view of the same.
Figs. 3 and 4 are detail views showing different ways of mounting the carbon-
contacts or electrodes.
Fig. 5 is a detail view of still another modification.
Fig. 6 is a detail view of another modification, and
Fig. 7 a detail view of electrode adjusting devices.
Referring to these figures:-
A is the door of an ordinary telephone transmitter box, or the frame in which
the diaphragm B is mounted. The diaphragın is rectangular in shape and is
confined at the top and bottom only by cleats or straps b. I preferably make the
diaphragm of wood, but of course any other suitable material may be employed.
A block C, also preferably of wood and extending transversely across the
diaphragm, is secured thereto, as clearly illustrated in Fig. 2, and by the dotted
lines in Fig. 1. This block carries the diaphragm electrode D which is in Fig. 1
shown as a continuous carbon rod. The opposing swinging pendent electrodes E
which rest lightly by gravity in contact with the bar D are in Fig. 1 each shown
as mounted on a bearing pin carried by a metal bracket F, all the brackets being
bolted to a common metal cross-bar G which is secured at each end to the frame A.
Price 71

page_text: It will be perceived that the pendent swinging electrodes E are mounted upon a
hinge or pivot bearing located in a vertical plane between that of the diaphragm
and the outer face of the carbon electrode or rod D, so that the ends of the pendent
electrodes rest lightly by gravity upon the bar D.
The drawings show a full-sized instrument, and I prefer to employ twelve
pendent electrodes as illustrated. Such a number of cylindrical polished carbon
pendants resting upon the cylindrical polished carbon electrode or bar D give a
resistance in the circuit most favorable for the transmission of speech.
As the
By mounting each pendant in an independently removable bracket any one of
the pendants may be changed without interfering with the others.
diaphragm B is unconfined at the side edges and the electrode D extends entirely
across the diaphragm, the amplitude of vibration of the diaphragm is the same at
all points in the transverse line in which the carbon D is secured on the diaphragm.
I therefore obtain a large variation of contact and a corresponding increase in the
amplitude of the electric waves or undulations. As the pendent electrodes are
supported by bearings located above the electrode D and only slightly in front
thereof, the vibration of the electrode D causes variations of contact between itself
and the pendent electrodes without producing any grating or scraping action.
I have found that by employing a cylindrical rod D and cylindrical pendants E,
and polishing them so that they have a smooth hard surface I eliminate entirely
from the surface any disturbing influence which would arise from the contacts of
the surfaces where ordinary unpolished carbon is employed.
g represents the primary circuit of the induction coil I, one pole of the local
battery LB being connected with the rod G which supports the pendants, and the
other with the electrode D. Instead of supporting the pendants upon independent
brackets, as shown in Figs. 1 and 2, an arrangement such as that shown in Fig. 3
may be employed in which the twelve pendants are divided into groups, each
group being pivoted upon a metal bar h mounted in lugs on the common supporting
bar G. Or the pendants may be supported as illustrated in Fig. 4, in which they
are all strung upon a metal rod h which is supported at each end by brackets G G
mounted on the frame. Or the pendants may be supported as shown in Fig. 6 in
which a carbon bar i mounted in brackets, as illustrated in Fig. 1, may have the
pendent electrodes strung upon it.
The carbon pivot will not oxidize, and the surfaces of contact between it and the
swinging electrodes are kept of a uniform resistance. Such a construction gives a
clear and distinct articulation.
Instead of employing a single bar-electrode D, mounted upon the diaphragm,
I may employ a series of pieces of carbon d, preferably cylindrical, each indepen-
dently mounted on the block C and having a corresponding pendent electrode E
resting upon it. All the blocks d are connected as clearly shown in the primary
circuit g.
If desired, of course, some means for adjusting the contacts of the telephone may
be employed, that is, the bar or frame carrying the pendent electrodes may be
adjusted to vary the angle of the pendants to the electrode carried by the
diaphragm. I do not however limit my invention to any such device. Obviously
a great many different forms may be used; as, for instance, an arrangement such
as that shown in Fig. 7 may be used. In that figure the bar or frame on which
the pendent electrodes are hinged may be supported at each end in the ends of
plate springs J mounted on the frame. These springs normally press the bar or
frame carrying the electrodes towards the diaphragm; but it may be adjusted
away from the diaphragm by means of the screws I, which pass through the
springs and bear upon the frame, as will be obvious.
Figure 8 is an elevation of the rear face of the transmitting diaphragm and the
electrodes carried thereby.
Figure 9 is an edge view of the same; and
Figures 10 and 11 are similar views showing the device for adjusting the gravity
electrodes.

page_text: Referring to these figures-
A is the diaphragm which is preferably rectangular, and may be made of any
suitable material, though preferably of wood.
A series of swinging electrodes a are shown as pivoted upon a bar b mounted on
a bracket B secured on the diaphragm, as shown. The bar b is preferably of
carbon, though it may be of metal. One end of the primary circuit of the
induction coil is connected with the bar b by a wire x. These swinging pivoted
electrodes rest upon a transverse carbon electrode C carried by a bracket c
arranged across the diaphragm preferably about at its centre. The electrode C is
connected by wire z with the primary circuit of the induction coil.
This apparatus is all of the simplest construction; is not liable to derangement;
and does not require adjustment. The number of swinging electrodes may be
increased or decreased if desired. The diaphragm may be secured at the top and
bottom as described in my application above mentioned, or may be secured at one
of its edges only, and is illustrated in Figs. 10 and 11 as secured rigidly at its
upper edge to a support F. The carbons are all preferably highly polished, so that
a smooth clean contact is obtained. With an instrument thus constructed the most
delicate sounds as well as the loudest will be accurately transmitted without any
rattle or grating in the instrument.
I have said that no adjustment of the instrument was necessary, and this is so
for all ordinary uses. In order, however, to meet all contingencies and provide for
the adjustment of gravity pressure between the pivoted electrodes and the trans-
verse electrode bar C, I have shown an arrangement illustrated in Figs. 10 and 11,
but of course any other suitable structure adapted for the purpose may be
employed. In this arrangement the bracket B, carrying the bar b to which the
swinging electrodes are pivoted, is itself pivoted in bearings or lugs L L secured
on the diaphragm, as clearly shown.
A blunt ended adjusting screw D, which bears against the diaphragm, works
through an arm b¹ on the bracket B. By this means the bar b, to which the
pendent electrodes are pivoted may be moved nearer to or further from the
diaphragm, so as to vary the pressure with which the pendent electrodes will lie
upon the transverse electrodes C.
A bent or plate spring E, secured upon the pivoted bracket B, bears against the
diaphragm, as clearly shown in Fig. 11, so as to hold the parts in their adjusted
position.
I have found by experiment that a rectangular diaphragm, supported rigidly at
one edge only, operates in a very advantageous manner, and I therefore consider
that feature important. I am aware that it has been proposed to suspend or
support a diaphragm at one side or edge by yielding or spring support, and do not
therefore claim such subject-matter.
By mounting the electrodes in a support pivoted near the upper or confined
edge of the diaphragm, the pivot of the pendent electrodes partakes of a com-
paratively small amplitude of vibration; while the electrode secured lower down
on the diaphragm, being further removed from the center of vibration, partakes of
a much greater amplitude of vibration. Excellent results are produced by such an
organization.
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
1. The combination of the diaphragm, the electrode carried thereby, the pivoted
pendent carbon electrode or electrodes which make contact with the electrode
of the diaphragm, and a carbon pivot or bearing on which said carbon electrodes
are mounted.
2. The combination of the non-adjustable stationary diaphragm, the transmitting
circuit, the opposing electrodes one of which is pivoted upon a movable pivot or

page_text: support, and means for changing the position of the pivot of said electrode
independently of the diaphragm to vary the pressure between the electrodes.
3. The combination in a telephone transmitter, of a swinging, hinged, or pivoted
carbon electrode, and a carbon pin or bearing on which it is hinged.
4. The combination of the diaphragm, a series of pivoted pendent swinging
electrodes formed of cylindrical pieces of carbon which are bored or perforated at
their ends to form their bearings, the carbon rod on which said electrodes are
pivoted, and an opposing electrode upon which they rest by gravity.
5. The combination of the diaphragm, an elongated electrode bar having a
curved or circular face secured upon the diaphragm, and a series of pivoted freely
swinging pendent electrodes having curved or circular contact faces, and a pivot
bar supported upon the diaphragm which passes through the upper ends of said
electrodes and on which they have their pivotal bearing, said pendent electrodes
resting by gravity upon the transverse electrode secured on the diaphragm,
substantially as and for the purpose set forth.
6. The combination of the diaphragm, the series of pivoted pendent gravity
electrodes carried by the diaphragm, the opposite electrode or bar secured upon
the face of the diaphragm, and adjusting mechanism for simultaneously changing
the position of the pivots of all of the pendent electrodes, whereby the force of
contact between the opposing electrodes is varied.
7. The combination of the diaphragm, the pivoted gravity electrode carried by
the diaphragm, the opposite electrode secured upon the diaphragm, and adjusting
mechanism for changing the position of the pivot of the gravity electrode, whereby
the force of contact between the opposing electrodes is varied.
8. The combination of a rectangular diaphragm, a support in which the
diaphragm is rigidly connected at its upper edge only and is left free to vibrate at
its other edges, one or more pendent gravity electrodes pivoted upon a support
carried by the diaphragm near its upper edge, and an opposite electrode or bar
upon which the pendent electrodes rest secured upon the diaphragm below the
support in which the pendent electrodes are mounted.
9. The combination of the diaphragm, a cylindrical carbon electrode arranged
transversely across the diaphragm, and pendent cylindrical carbon electrodes which
rest by gravity on the electrode on the diaphragm.