A New or Improved Telephone Transmitter.
Year: 1892

page_text: Date of Application, 23rd Aug., 1892
Complete Specification Left, 13th Feb., 1893-Accepted, 20th May,
1893
PROVISIONAL SPECIFICATION.
A New or Improved Telephone Transmitter.
We, ERHARD LUDWIG MAYER, of 11 Billiter Square, London, and ALEXANDER
CHALMERS JAMESON, of the Whitehall Club, Westminster, both in the County
of Middlesex, Engineers, do hereby declare the nature of this invention to be as
follows:-
Our invention relates to a new or improved telephone transmitter by which
certain advantages are obtained.
In carrying our invention into effect we attach to the diaphragm a support of
insulating material to the back and to the front parts of which we affix conducting
pieces constituting the fixed microphonic element hereinafter to be described.
Lying loosely upon the said support we have two conducting pieces constituting
the movable element and we so shape the base of the support or the part on which
the said pieces rest that they shall each press against the corresponding conducting
piece of the fixed microphonic element that is to say so that one of the movable
pieces hereinafter termed the front movable piece shall press against the front
fixed piece and the other movable piece hereinafter termed the rear movable piece
press against the rear fixed piece.
In conjunction with these elements we employ an induction coil having two
primary windings the one winding having its circuit through the rear movable
piece and the rear fixed piece and the other having its circuit through the front
inovable and the front fixed pieces. The said primaries we connect up in such
manner that the current from the transmitter battery will traverse them in opposite
directions.
The action of our apparatus is as follows. When movement inwards of the
diaphragm takes place the inertia of the movable pieces causes increased pressure
between the front movable piece and the front fixed piece and decreased pressure
between the back movable piece and the back fixed piece, so that the current
traversing the primary winding which has the front pieces in circuit will be
increased and that traversing the primary winding which has the back pieces in
circuit will be decreased.
In a similar manner movement of the diaphragm in the other direction will
cause increased pressure between the rear movable piece and the rear fixed piece
and decreased pressure between the front movable piece and the front fixed piece
so that the current traversing the primary winding which has the back pieces in
circuit will be increased and that traversing the primary winding which has the
front pieces in circuit will be decreased. It will thus be seen that movement of
the diaphragm in each direction causes simultaneously increase of pressure and
decrease of pressure instead of as in the usual forms of transmitter increase of
pressure when there is movement in one direction of the diaphragm and decrease
of pressure when there is movement in the other direction. A doubled effect is
thus produced and an increased action is obtained in the secondary circuit and
consequently in the receiver in the said secondary circuit. There are two double
cycles of operation in my transmitter instead of two single cycles as is usually the
case.
In order to increase the effect we may employ a weight resting upon the two
movable pieces herein before referred to and for this purpose we may select a
weight of such form that its centre of gravity will be as high above the movable
pieces as is convenient.
We have spoken of the support or piece on which the movable conducting
pieces rest being of such shape as to produce pressure between them and the fixed

page_text: conducting piece. We have also referred to the use of a weight resting upon such
movable pieces. In practice, when we employ such a weight we may sometimes
rely upon it to cause the initial pressure between the movable and fixed conducting
pieces instead of obtaining such pressure through the shape of the support or piece
on which the movable conducting pieces rest.
We have hereinbefore spoken of the employment of a single induction coil
wound with two primaries, current from the transformer battery being sent through
the said primaries in opposite directions. We may however instead of employing
such an induction coil employ two separate induction coils of the ordinary type
that is to say having one primary and one secondary winding upon each. When
we employ two induction coils in this way we pass currents through each of their
primaries in opposite directions that is to say the current through the primary of
one induction coil and the back clements in one direction and the current through
the primary of the other induction coil and the front elements in the opposite
direction. Or, we may pass the currents through the primary windings of the two
induction coils in the same direction, but in this case it is necessary that we
connect up the secondary windings of the two induction coils in opposite directions
so that the induced currents will traverse them in the same direction.
Dated this 23rd day of August 1892.
E. L. MAYER,
A. C. JAMESON,
Per J. G. L.
COMPLETE SPECIFICATION.
A New or Improved Telephone Transmitter.
We, ERHARD LUDWIG MAYER, of 11 Billiter Square, London, and ALEXANDER
CHALMERS JAMESON, of the Whitehall Club, Westminster, both in the County of
Middlesex, Engineers, 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 :-
Our invention relates to a new or improved telephone transmitter by which
certain advantages are obtained.
In telephonic transmitters of the ordinary type the movement of the diaphragm
backwards and forwards (inwards and outwards) under the influence of the sound
waves impinging upon it, increases and decreases the pressure, or intimacy of
contact, between the carbon elements, increase being produced by movement in one
direction, and decrease by movement in the opposite direction. In this case there
is what I shall term a single cycle of operations or effects.
This type of instrument may be diagrammatically illustrated in Figure 1 of the
accompanying sheets of drawings. In this figure A is the diaphragm, B one carbou
element attached to the diaphragm, and C the other carbon element attached to the
fixed or yielding support D. In this case it will be seen that an inward or back-
ward movement of the diaphragm (that is to say a movement from left to right in
'the figure) will cause increase of pressure, or of intimacy of contact, between the
elements B and C ; whilst movement of the diaphragm forwards or outwards (that
is to say from right to left in the figure) will produce a decrease of pressure or of
intimacy of contact, between the elements B and C.
The majority of telephone transmitters belong to the above type, which as we
have said, we term the single cycle type.
As telephonic invention proceeded it was seen that the action might be duplicated,
so to speak, and that the movement of the diaphragm in both directions might be
employed to produce both increase and decrease of pressure, or of intimacy of
contact, and what we shall term double cycle instruments then came upon the field,
that is to say transmitters in which there are two cycles of operations or effects.
A good type of this class of instruments is diagrammatically represented in
1

page_text: Figure 2 in which A is the diaphragm and B and C two carbon pieces carried by
the insulating U-shaped support D attached to the diaphragm. Between B and C
is a wedge shaped conducting piece E attached to the case of the instrument by a
yielding support, such as a spring (as is shown at F in the present case), or to a
heavy weight suspended from a part of the case.
With this type of transmitter induction coils having two primary windings and
one secondary winding are employed, instead of the usual form of induction coil in
which there is one primary winding and one secondary winding. Such an induction
coil with two primaries is shown at G; and it is used with the parts hereinbefore
mentioned as follows: The one pole of the battery H is connected by the wire h
to the central conducting piece E, whilst the wire from the other pole splits up into
two branches and, the branch including in its circuit one of the said primary
windings of the induction coil and the carbon piece C; whilst the other branch ²
includes in its circuit the other primary winding of the induction coil and the other
carbon piece B. These primaries are so wound that the current flows in opposite
directions through them. The secondary winding j. j. is connected to line J and
earth J in the usual manner.
It will be seen from the figure that instruments of this type duplicate the action
of those of the single cycle type. Let us assume that the diaphragm moves from
left to right. The pressure or intimacy of contact between B and E is increased
and that between C and E decreased. Similarly, when movement in the opposite
direction of the diaphragm takes place, the pressure between C and E is increased
and that between B and E decreased. As increase of current accompanies increase
of pressure, or of intimacy of contact, it will be seen that at each movement of the
diaphragm, either in one direction or in the other, there will be increase of current
in one primary and decrease of current in the other; but as these alterations of the
current flowing in the said primaries act in an inverse sense on the secondary
winding, it is obvious that an increased effect is obtained. Instruments of this
type we term double cycle instruments.
Our invention is as much an improvement on the double cycle instruments as
these are upon the single cycle instruments and our instruments constitute what
we may term four-cycle instruments.
:
22
In carrying our invention into effect, we attach to the centre of the diaphragm
support on which are fixed two pieces of carbon, one being fixed to the front part
of the support and the other to the back part of the support. These two fixed
pieces, which may be duplicated when desired, we shall hereinafter refer to as the
front fixed piece and the rear fixed piece. Between the said fixed pieces rest two
pieces of carbon hereinafter termed the movable pieces. These pieces are of such
shape, cylindrical for example, that they are free to vibrate or roll within minute
limits. One of these, hereinafter termed the front movable piece, is in contact
with the front fixed piece; and the other, hereinafter termed the rear movable
piece, is in contact with the rear fixed piece. In addition to the said pieces we
employ a device which we shall hereinafter term a "presser," whose function is to
preserve contact between the front movable piece and the front fixed piece, and
between the rear movable piece and the rear fixed piece. This presser may take
the form of a weight resting upon and between the movable pieces, or it may take
the form of the roof-shaped piece on which the movable pieces rest.
In conjunction with these elements we employ an induction coil, similar to that
hereinbefore described with reference to double-cycle transmitters, that is to say
having two primary windings, the one primary having its circuit through the rear
movable piece and the rear fixed piece, and the other primary having its circuit
through the front movable and the front fixed pieces. The said primaries we
connect up in such manner that the current from the transmitter battery will
traverse them in opposite directions.
Figures 3, 4, and 5 illustrate our invention on a slightly enlarged scale, Figure 3
being a vertical section, Figure 4 an elevation, and Figure 5 a plan. The
diaphragm and the induction coil with its circuits are shown only in Figure 3.

page_text: A, is the diaphragm and B the insulating support, in this case having the shape of a
box or trough, the said support being attached to the diaphragm by a minute screw
and nuts. In the case illustrated, the front and rear fixed pieces C and C² respec-
tively, are duplicated. D' is the front movable piece and D2 the rear movable
piece. E is the weight hereinbefore mentioned, acting as a presser and consisting
preferably of brass, though any other conducting material will answer the purpose.
F is the bottom of the support constructed of the form of a roof and acting also as
a presser. In practice we prefer instead of shaping the bottom of the support so
that it will act as a presser as aforesaid, to form the said part of conducting
material, usually carbon, so that instead of attaching the wires to D1 and D2, we
can attach a wire to F for the purpose of completing circuit through D1 and D2.
It will be seen from Figure 3 that the induction coil and its circuits are similar to
those hereinbefore mentioned with reference to double cycle instruments, the two
primary windings branching from one pole of the battery.
The action of our apparatus is as follows: When movement inwards of the
diaphragm takes place (from left to right of the figure) the inertia of the movable
pieces causes increased pressure between the front movable piece and the front
fixed piece, and decreased pressure between the rear movable piece and the rear
fixed piece, so that the current traversing the primary winding which has the front
pieces in circuit will be increased; and that traversing the primary winding, which
has the back pieces in circuit, will be decreased. In a similar manner, movement
of the diaphragm in the other direction will cause increased pressure between the
rear movable piece and the rear fixed piece, and decreased pressure between the
front movable piece and the front fixed piece, so that the current traversing
the primary winding which has the rear pieces in circuit will be increased, and that
traversing the primary winding which has the front pieces in circuit will be
decreased. A doubled effect similar to that in double cycle instruments thus takes
place. But this is not the whole action. Whilst the diaphragm moves inwards
(left to right in the figure) it will be seen that the presser acts as a shunt
circuit, and brings in another series of operations. Instead of the variations of
current depending simply upon increase of pressure between the front pieces,
and decrease of pressure between the rear pieces, when the diaphragm
moves inwards, and vice versa when it moves outwards, we get an additional
variation added so to speak to the other, as we shall now describe. Let
us assume that the diaphragm is moving inwards. The current through D'C' is
increased, and that through DC2 decreased, by a certain amount due to the
difference of pressure between the parts. But the lessening of the pressure
between D and C2 will cause a part of the current flowing through the said
parts to be shunted through the presser to D' and thus be added to the current
passing through D' C'; so that the current passing through D'C' will not only
be augmented by the current due to the increased pressure between D' and C³,
but it will also be augmented by a currect shunted through the presser as
aforesaid. Similarly, when movement in the reverse direction of the diaphragm
takes place, part of the current through D' C¹ will be shunted through the
presser to D2, and augment the current through D C already augmented by the
increased pressure between D² and C².
It will thus be seen that in our instrument a new double cycle of operations
is brought into play, and that greatly increased effect is obtained.
In addition to obtaining such increased effect as aforesaid, it is obvious that it is
necessary to have extreme delicacy, and for this purpose we have attached the
whole of the microphonic elements to the diaphragm, so that they may vibrate
therewith and we have arranged the said elements in tandem, as it were, that is
to say, one in front of the other, so that they may be as near as possible to the
centre of the diaphragm, and attached only to the said centre.
With reference to that form of presser which consists of the weight resting upon
the movable pieces, it will be noticed that the centre of gravity is as high as is
-convenient above that of the movable pieces, and that the centre of gravity of

page_text: these movable pieces is as high as convenient above their points of contact with the
fixed pieces. We find this an advantageous construction and we also find it advan--
tageous to surround the weight presser with two rings of platinum wire, to prevent
any corrosion or undue alteration of contact between the said weight presser and.
the movable pieces. Figure 6 represents on an enlarged scale such a weight.
presser with the said platinum rings affixed thereto.
The following are constants of certain parts of one of our instruments: Movable.
pieces (cylinders) each 91 millimetres in length, 6 millimetres in diameter, and.
6 grains in weight. Weight presser, consisting of cylinder of brass, 9 millimetres.
in length, 4 millimetres in diameter, and 21 grains in weight. Rings of platinum
wire, of millimetre in diameter. The angle of the roof shaped presser equals.
150 degrees. With these parts I generally employ a diaphragm of ebonite about.
three inches in diameter and of a thickness of about No. 19 of the standard gauge..
I generally make the support B of ebonite and as light as possible. The distance-
between the geometric axes of the two movable pieces is 7 millimetres.
Having now particularly described and ascertained the nature of the said inven-.
tion and in what manner the same is to be performed, we declare that what we.
claim is:
1. The new or improved four-cycle telephone transmitter substantially as set
forth.
2. In a telephone transmitter the combination of two fixed pieces, two movable-
pieces, and a presser of conducting material; substantially as and for the purpose-
set forth.
3. In a telephone transmitter the use of a presser acting as a shunt, substantially-
as and for the purpose set forth.
s and for the purpose set forth.
Dated this 11th day of February 1895.
For the Applicants,
J. G. LORRAIN, M: Inst. E.E., &c.,
Norfolk House, Norfolk Street, Strand, London, W.C.,.
Chartered Patent Agent.