IMPROVEMENTS IN ELECTRICAL APPARATUS FOR THE TRANSMISSION OR REPRODUCTION OF SOUND
Year: 1881

page_text: . LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London; for an Invention
of "IMPROVEMENTS IN ELECTRICAL APPARATUS FOR THE TRANSMISSION OR
REPRODUCTION OF SOUND." A communication from abroad by Amos Emerson
Dolbear of Somerville. Massachusetts. United States of America.
COMPLETE SPECIFICATION filed by the said William Robert Lake at the
Office of the Commissioners of Patents on the 29th March 1881.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN ELECTRICAL APPARATUS
FOR THE TRANSMISSION OR REPRODUCTION OF SOUND." A communication from
abroad by Amos Emerson Dolbear, of Somerville, Massachusetts, United States of
America.
This Invention relates to improvements in apparatus for the transmission of
sounds by electricity. The said Invention comprises the mounting of one or both
of the terminals of a secondary coil in a case, in such a manner that sounds acting
upon any suitable transmitter in the primary coil will be reproduced by the
vibrations of one of the terminals or by the vibrations of a body which is caused to
vibrate by one of the terminals. The said Invention also comprises an improved
transmitter, hereinafter described. The said Invention also relates to the system
or method of connecting two or more receivers and two or more transmitters for
practical use; and comprises the combination of two induction-coils, two receivers,
and two transmitters in a novel manner, as also hereinafter described.

page_text: series of receivers.
Figure 11 is a perspective view of my improved transmitter, and
Figure 12 is a central section of the same.
Figures 13, 14, and 15 represent in section various forms of portions of the said
transmitter hereinafter described.
Figure 16 represents one method of combining two of the said transmitters.
A represents the receiver, whose case is shown in Figure 3, as made up of three
pieces, namely, a back piece r, an ear-piece s, and an annular piece t which serves
to connect the pieces r and s. a, b, are thin elastic or yielding plates, preferably of
iron, forming terminals of the secondary coil of an induction coil. These plates are
securely retained or held at their edges and are brought very near to each other,
but not in contact, a thin annulus or flange d lying between them. This flange is
preferably formed on the interior of the connecting piece t, the terminals a, b, being
placed on opposite sides of the said flange, as shewn. The ear-pieces of the case
holds the terminal a in place with the proper tension around the edge to ensure
mass vibrations of that terminal. The terminal 6 is held in place by the back
piece of the case. Each of the plates a and b is formed with a small tongue
similar to that shewn at a² in Figure 4, with which tongue the binding screws are
connected, as shown. By the use of these tongues an even pressure around the
whole edge of the plate is possible. In this receiver the plate a is connected with
one end of the secondary coil, and the plate b with the other end of that coil.
The adjustment of the instrument is effected by the screw A³, and this screw by
contact with the back-plate b prevents any vibrations of that plate which would
interfere with the proper vibrations of the front plate a.
This Invention necessitates the use of electricity of a very high electro-motive
force, and this is best obtained by means of a secondary coil with a high resistance,
the best results having been obtained from four or five thousand ohms. of No. 36
copper wire. Transmitters such as are in common use will answer with the said
receiver, but the best form of transmitter is that shown in the Drawings, and
hereinafter fully described.
In the receiver above described both terminals of the secondary coil are used, but
as only one terminal is essential three other forms of my receiver are shown in
Figures 6 and 7 of the Drawings.
In each of these receivers the casing is formed of three pieces, as above described,
r being the back-piece, 8, the ear-piece, and t the piece which connects the pieces r
and 8.
The plate a of the receiver I is a thin elastic disc, preferably of iron, and
similar to that above described; the vibrations of this disc reproduce the sound
which causes the diaphragm of the transmitter T to vibrate. This transmitter
may be of any suitable construction, but I prefer the form shown in the Drawings
and hereinafter described; the said transmitter and the battery B are in circuit
with the primary coil, as will be understood without further description.
In the receiver I the plate a serves as one terminal of the secondary coil F, and
any change in the electrical state of the latter varies the potential of this plate a,
and causes it to attract the plate b, which is mounted close to but not in contact
with the said plate a, but as the plate b in the receiver I is so mounted that it
cannot vibrate, the plate a will vibrate as its potential varies. In this receiver I
the plate b, the back piece r, and the adjusting screw u are all of metal. It will
be seen that neither the plate b, the back piece r, nor the screw u of the receiver I
is connected to the coil F, but that only one terminal of the coil F (namely the
plate a) forms any part of the receiver I. The plate b may be made in one piece
with back-piece r, but for purposes of adjustment it is preferably made as shown.
The force of the attraction between the charged terminal a and any neighbouring
body is slight, unless the neighbouring body is many times larger than the terminal
and is itself capable of being readily electrified, and for this reason, when the
neighbouring body is a plate (as it is preferably made for purpose of adjustment),
it should be electrically connected with a larger body, consequently the back-

page_text: piece r of the case of the receiver I is made of metal, and is in metallic contact
with the plate b; the neighbouring body which is attracted by the plate a in the
receiver I, being in fact the plate b, the piece r, and the screw u, which, being all
of metal, as above stated, and in metallic contact, act as one body in the said
receiver I; but, as will be clear, the back-piece r, the plate b, and the screw u may
be one single piece of metal, and some other provision be made for the necessary
adjustment.
In the receiver II the terminal a is mounted upon the back-piece r, so that it
cannot vibrate and must therefore be insulated, consequently the back-piece ris
made of hard india-rubber. The plate b, which is the neighbouring body in this
receiver II, is connected by the wire 62 with a metal band or ring upon the back
piece r, in order to increase the attractive force due to the electrification of a greater
mass than the plate b, and without interfering with the proper vibration of the
latter, which in the receiver II vibrates as the potential of the terminal a varies.
It will be understood that either of the plates b may be grounded, so as to
increase the electrification of these plates, but it is not necessary to ground either
of the said plates, as the audibility of the sounds reproduced is practically as great
when the back-piece of the receiver is held in the hand as when the plates b are
both grounded, and it makes no difference whatever whether both be grounded or
only one. In other words the receiver I will reproduce articulate and other sounds,
even if the back-piece ? be of hard india-rubber or other non-conducting material
and the plate 6 be wholly disconnected from the coil F, but the sounds reproduced
are faint although distinct and audible; the sounds will be louder if the piece r be
of metal, as above described, or if the plate 6 or metallic piece r be grounded, but
the difference is very slight, the sounds being practically as loud when the metal
piece r is used as when the plate b is grounded. The sounds of the receiver II are
likewise distinct and audible when the wire 62 and metal band 3 are omitted, but
are louder when the metal band 2 and the wire b² are used, as shown, or when the
plate 6 of the said receiver is grounded. Moreover, the reproduction of sound by
the receiver I. does not depend at all upon the grounding of any part of the
receiver II, as the receiver I will act with the plate b of the receiver II not
grounded, precisely as it does when the plate b of the receiver II is grounded, and
the receiver II will act when the plate b of the receiver I is not grounded,
precisely as it acts when that plate of the receiver I is grounded.
Instead of making the plate b of metal and connecting it metallically with the
back-piece or the band r², it may be made of any non-conducting material, and
in this case the increased loudness is produced by electrifying the plate b before it
is put in place, or as shown in the receiver III, where b is an india rubber plate
and 63 is a disc of felt attached to the hard india-rubber support 6, which is turned
by the thumb and finger to electrify the india-rubber plate 6 by friction.
A series of receivers, such as those above described, may be arranged as indicated in
Figures 8, 9, and 10, which indicate different arrangements of receivers A2, A3, A³,
with the coil F.
The main advantages of this Invention are that it is not appreciably affected by
ordinary induced currents on the line; it has no magnet to deteriorate, the adjust-
ment is more simple, is not affected by barometric and hygrometric variations,
and lacks the fine wire helix of the common receiver, which is very liable to get
out of order. It is very efficient also on very long lines.
The best system for the practical use of this Invention is illustrated in Figure 5,
and the best form of apparatus is that shown in Figures 1 and 2. In these Figures
A, A, represent the receivers, T the transmitters, B the batteries, F the induction-
coils, and G the switches. The transmitter T and battery B are in the circuit with
the primary coil of the induction-coil F, and this circuit is completed when the
transmitter is to be used by throwing over the member or part g of the switch G
until it makes contact with the member g¹, thereby completing the battery-circuit
through the transmitter and primary coil. The electricity induced in the secondary
coil affects the plates in the distant receiver by means of that branch of the wire m'

page_text: which extends from one end of the secondary coil to the member g of the switch G,
the members g, g, the line wire l, which is a continuation of the member g, the
wire, which is a branch of the line wire Z, the receiver wires a¹, b', the wire m²,
the members g, g³, of the switch G, the wire n³ to earth, thus cutting out the receiver
at the sending station (on the left of the diagram) and the secondary coil on the
right of the diagram.
When the sending station is the one at the right of the diagram the switch G at
the right will be arranged similarly to the switch G at the left, and the receiver at
the left is electrified by means of the wire l', the receiver wires a¹, 61, (at the left
of the diagram) the wire m³, the members' g, g³, of the switch G (at the left of the
diagram), the wire n' to earth.
The switch G is composed of two springs g, g², and two stops g³, g³, arranged as
shown, so that when the spring g is brought in contact with the stop g' it will
also be in contact with the spring g², and when the spring g is in contact with the
stop g³ it will be out of contact with both the spring g* and the stop g¹.
One end of the secondary coil on the left of the diagram is connected with the
spring 9 on the left of diagram by means of one branch of the wire m', and with
the receiver-wire 6' on the left of diagram by means of the other branch of the
wire m³, and one end of the secondary coil on the right of the diagram is connected
with the spring g on the right of the diagram by means of one branch of the
wire m³, and with the receiver-wire 61 on the right of the diagram by means of the
other branch of the wire m².
<<
I am aware of the apparatus which is mentioned as used by Dr. Wright in
Ferguson's Electricity," published by William and Robert Chambers, of London and
Edinburgh, in 1867, pages 258 and 259, in which two sheets of paper silvered on
one side were placed back to back and connected with the two ends of an induction
coil, the primary circuit of which contained a Reis' transmitter, and I therefore lay
no claim to that apparatus. The receiver constructed according to this Invention
differs therefrom in that the sounds transmitted are reproduced by mass-vibrations,
while in the "Wright" receiving apparatus the sound produced was mainly, if not
altogether, due to moleular motion and not to mass vibrations; moreover, Wright's
sheets of silvered paper were so arranged that each would damp any mass vibra-
tions of the other. And in his apparatus any slight mass-vibrations, even if not
wholly damped, would be necessarily so irregular as to be worthless as a means of
reproducing sounds; the fact also that the mass vibrations of each sheet damped
those of the other sheet would make all the mass-vibrations worthless for this
purpose.
I am also aware of English Patents, No. 4934, of 1877, and No. 2396, of 1878,
and lay no claim to all therein shown.
I will now proceed to describe my improved transmitters which are illustrated
in Figures 11, 12, 13, 14, and 15, and in Figure 16, which latter Figure illustrates
one mode of arranging or combining these transmitters so that one will act as a
receiver when the other is used as a transmitter, as this instrument although
especially adapted for use as a transmitter may also be used both as a receiver and
transmitter.
The said instrument consists of a diaphragm K mounted vertically in a suitable
standard K. This diaphragm may be made of any thin sheet material of sufficient
strength, whether a conductor or non conductor. I prefer to make the diaphragm K
of thin sheet metal such as is ordinarily used in telephones, and to connect the
wire k with the edge of this metal diaphragm may be a stout plate of carbon, or
may have the carbon nipple 2 secured to it; or the diaphragm may be independent
of the circuit as illustrated in Figure 14. My Invention does not relate to the
material of which the diaphragm is formed or to the manner of connecting it with
the terminal k². The terminal is supported by the hanger J so that it may bear
against the terminal k². The force with which this terminal bears against the
said terminal k² depends, when the hanger J and terminal are of a given weight,
upon the position of the centre of gravity of the hanger J including the terminal k³

page_text: supported by it so that the weight of the said hanger J and terminal ³ may be
large, and yet the terminal ³ will be pressed very lightly against the terminal k³;
moreover a change in the centre of gravity of the hanger J will increase or decrease
the pressure of the terminals one upon the other. The hanger J, in Figures 11,
12, 15, is provided with the screw stem j and the nut j¹, whereby the pressure
of the terminal ³ upon the terminal k may be regulated with the utmost
accuracy.
Both the electrodes or terminals k², k³, may be formed of carbon, or one of metal
and the other of carbon, or both of metal, but in the latter case the terminals tend
to be fused together; it is better therefore to have one of them carbon or some
like material.
The hanger J may be electrically connected with its support i by mercury
cups, as shown in Figure 11, or it may be connected by a flexible wire o, as in
Figure 15, the wire being so flexible as not to affect materially the operation of
the hanger; or the electrodes may be insulated from its hanger J, as illustrated
in Figure 14, where p is a sleeve of hard india-rubber. The circuit wires k, k¹,
are so flexible in this case also as not to materially affect the operation of the
hanger.
If one of the said instruments be arranged in the primary circuit of an induc-
torium or induction coil and another in the secondary circuit, sounds, including
words spoken at the diaphragm of the first instrument, will be reproduced by the
second instrument. If two or more of my instruments be in the same circuit
each will act as a transmitter or receiver.
The method of arranging the instruments as shewn in Figure 16 gives good
results. In this Figure the circuits k, k', F, and k, k¹, F¹, are arranged to act as
both primary and secondary circuits; the circuit k, k¹, F, being the primary circuit
and the circuit k, k¹, F¹, the secondary circuit when the instrument at X is used as
a transmitter, and the instrument at Y as a receiver, and vice versa. The induction
coils are arranged in such relation to each other (as will be well understood without
further description) that variations of the battery current through the coil F will
set up induced currents in the coil F¹, and thereby vary the battery currents in the
coil F, and so with regard to the coil F¹ variations in the battery current in the
said coil will cause induced currents in the coil F. When the instrument at X is
used as a transmitter the battery current in the circuit k, k³, F, is varied by the
vibrations of its diaphragm, and the induced currents set up in the coil F¹ cause
the diaphragm of the instrument at Y to vibrate in such a manner as to reproduce
the sounds which caused the vibration of the diaphragm of the instrument at X,
and when the instrument at Y is used as a transmitter the instrument at X is a
receiver.
The essential feature of this part of my Invention consists in the arrangement
of two or more circuits, each with a battery and an induction coil; all the
induction coils being arranged so that variation of the battery current through one
will cause induced currents in the others, and thereby vary the battery currents of
the others.
Having thus fully described the said Invention as communicated to me by my
foreign correspondent and the manner of performing the same, I wish it understood
that I claim,
-
First. The apparatus or instrument composed of the plates a, b, mounted in a
suitable case, and adapted to operate in combination with the secondary coil of an
induction coil, substantially as and for the purpose above set forth.
Second. The combination of two induction coils, the primary coil of each of
which is included in a circuit containing a battery, and a transmitter T with the
secondary circuits, each containing a receiver, and the switches G consisting of the
members g, g, g², g³, whereby the receiver at the sending station and the coil
at the receiving station are switched out of the line, substantially as and for the
purpose above described.
Third. The combination of a primary coil in circuit with a battery and a

page_text: transmitter and a secondary coil with its enlarged terminal a mounted in a suitable
case, and arranged to vibrate or to cause vibrations in the plate b, as and for the
purpose above set forth.
Fourth. The diaphragm K arranged vertically or substantially so, in the
standard K', the hanger J, and the electrodes k³, k³, all arranged and combined
substantially as and for the purpose herein described.
Fifth. The combinatoin of the coils F, F¹, each in circuit with a battery, and
each arranged to act as a primary coil while the other acts as a secondary coil,
substantially as and for the purpose herein specified.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Twenty ninth day of March, in the year of our Lord
One thousand eight hundred and eighty one.