Improvements in Electric Telephones, and Means of Signalling thereon.
Year: 1894

page_text: Date of Application, 24th Oct., 1894
Complete Specification Left, 23rd July, 1835-Accepted, 19th Oct., 1895
PROVISIONAL SPECIFICATION.
Improvements in Electric Telephones, and Means of Signalling
thereon.
ALFRED CHARLES BROWN of 129 Algernon Road Lewisham in the County
of Loudon, Electrician, and GEORGE RICHARD NEILSON of 50 Old Broad Street
London Secretary to Public Company do hereby declare the nature of this invention
to be as follows:
These improvements relate to the production of an electric telephone receiver
capable of giving a very clear and loud reproduction of articulate and other sounds
while retaining a small and compact form-to a means of signalling thereon (also
partly applicable to existing telephone systems)-and to a means of causing the
receiver coils to fulfil the functions of the separate induction coils heretofore used
in conjunction with the transmitters, at both ends of the line, so as to cut out
the waste resistance and self induction of the secondaries of the induction coils,
and so increase the current energy available to operate the distant receivers.
To fulfil the above objects we construct our telephone receiver preferably with
two diaphragms opposed to each other, having a ring or similar seating between
them forming a case, and on to which they are clamped by two end pieces, which
may be screwed over or into or otherwise affixed to the central ring seating, and
have recesses turned out so as to clamp the diaphragms round near their elges but
leaving a shallow chamber over the larger part of the surface of the diaphragms on
their outsides, which chambers are practically airtight.
The diaphragms are then actuated by an electro-magnet or electro-magnets,
placed between them, and affixed to the central ring seating, which seating also
carries on one side a mouthpiece communicating with the inside air space contained
between the two diaphragms. If one electro magnet is used it may consist of
a single coil and straight core, each end or pole of which acts on one diaphragm. If
more than one coil is used however care must be taken that they are joined in such
way that each diaphragm is attracted towards the centre or released away by the
same direction current as respectively attracts or releases the other diaphragm.
We then polarise the core of the electro-magnet, when a single straight one is used
as described above, by placing round the outside of the coil or coils of the electro-
magnet a tube of steel, preferably slit down one side, and magnetised as nearly to
saturation as possible so that one of its flat ends which faces a diaphragm is north
seeking and the other south seeking and the magnetic circuit is then completed,
less the small necessary air gaps, through the diaphragms themselves and the
central core of the electro-magnet, which together with the diaphragms is thereby
strongly polarised by induction. The steel tubular magnet may also if desired
itself form the central case or ring seating for the diaphragms. Or, if a separate
case be used, an equivalent of the tubular magnet may of course be made by arranging
a number of separate bar magnets round inside the case but outside of the coil of
the electro-magnet, with their similar poles all at the same end, and so that they
together practically form a laminated tube round the electro-magnet. The polarizing
magnets may also be bowed outwards in the middle to increase their length, projecting if
desired through the central casing. Or we may polarise the core of the electro-
magnet by connecting its central portion between the two diaphragms to the pole
of a steel magnet which may either extend straight away at right angles to the core
and project through the central ring seating so as to form a handle for the instrument,
or may be curved away round the outside of the coils but inside the casing so as
to get as great as possible a length and have its other end preferably but not

page_text: necessarily thickened so as to connect it more closely with both the diaphragms at
some point near their edges, two shorter coils being used in these instances, one
placed on each end of the cross core, so as to be opposed' one to each diaphragm,
and joined in circuit as heretofore described. Or we may use a horse-shoe magnet
opposed to each diaphragm, in which case the polarising magnet or magnets may
as before extend out at right angles through the case so as to form a handle, or
may be circular or approximately similarly curved, so as to lie around the outside
of the coils but inside the space contained within the central ring seating or they
may themselves form the ring seating, and with their poles extended inside towards
the cross cores and about midway between the diaphragms by pole pieces so as to
oppositely polarise each limb of the cross cores which extend from thence towards
the diaphragms, so as to form two horse-shoe magnets one opposed to each
diaphragm, four small coils being then used and all joined in circuit so as to fulfil
the above-mentioned condition as to attracting both diaphragms together.
In each of the above cases the object is to keep the polarising magnets, which
charge the cores of the electro-magnets, either within the space contained between
the two diaphragms and inside or else forming part of the substance of the central
ring seating, or casing, or else to arrange that the magnets shall form a convenient
central handle for the complete instrument.
66
The part of our invention relating to signalling consists in causing the receiver
(which for this purpose may be either as above described or any ordinary previously
used form) to emit a loud buzzing sound, capable of attracting attention from
a distance and useful for a variety of other signalling purposes, by one of the
following means. Where the instruments are used on private lines," or circuits
which do not communicate with an exchange, we screw through or otherwise affix
to some part of the case of the receiver opposite to the outside (or side farthest
from the electro-magnet) of the diaphragm, (or one of the diaphragms, if the
receiver have more than one) a metal contact screw, taking care that the body of
same is by any ordinary means insulated from the diaphragm itself. We then
connect this contact screw in series in circuit with the coils of the receiver, the
circuit being completed through the diaphragm of the instrument with which the
point of the said contact screw makes contact when properly adjusted, the contact
surfaces of both the screw and diaphragm being of course properly platinised.
When a direct battery or generator current is then passed through such a receiver
the diaphragm is vibrated electro-magnetically and so produces a loud buzzing
sound. If another receiver be joined in series or parallel circuit also, the latter
will likewise be caused to sound, and for this purpose it is not necessary to include
the contact of the first receiver in series with the second but only the coils, so that
the contact and coils of the first may be included in a local battery or generator
circuit, while the extra currents from the coils of the first are used to operate the
second or any number of other receivers, which arrangement, gives the maximum
of sound with the minimum current.
We also prefer to load the central portion of the diaphragm of the receiver
carrying the contact with a heavier piece of iron, which greatly increases the
loudness of the buzzing sound, and eases the adjustment, without appreciably
affecting, or decreasing, the loudness and clearness of the articulation of the
receiver for vocal telephonic sounds.
For "exchange circuits" however, or lines communicating with a central station
we prefer to produce the buzzing sound in the receivers at the subscribers, or out
stations, for signalling from the exchange or central station to the out stations,
(or similar purposes) by means of a powerful induction coil, placed at, or in
connection with the exchange, and having a rapidly interrupted battery or
generator current passed continuously through its primary, while the exchange is
operating, (or capable of being switched on or off at will). Arrangements are then
made by which the secondary of the induction coil is connected to the out station
circuits by the operators signalling keys, instead of the battery or generator
current heretofore used for actuating the bells or other signals at the out stations.

page_text: Or instead of an induction coil, an ordinary electro-magnet and make and break
may be used, kept going by a local current at the exchange, and the extra currents
from the coils of this electro-magnet put to the out station lines by the operators'
signalling keys, instead of the currents from the secondary of the induction coil.
In order to cause a telephone receiver to act as its counterparts induction coil
we may sometimes wind them with two different circuits, one having a low
resistance and being arranged to be connected in the local battery circuit together
with the transmitter when the instrument is in action, and the other having a high
resistance and being connected to line and to the distant receiver, so that the low
resistance circuit forms the primary, and the high resistance circuit the secondary
(as in ordinary induction coils) as well as actuating the receiver's own diaphragm
or diaphragms.
The two coils or circuits may be variously disposed on their respective cores,
as for instance wound one underneath the other in the ordinary way, but are better
wound as separate coils and placed upon different parts of the length of the same
core, so that while the primary or low resistance circuit can act inductively on the
secondary or high resistance circuit, the latter occupies the position of closer
proximity to the diaphragm or diaphragms, and is therefore more efficient in
vibrating it or them, in response to currents received from the line.
The form of receiver which we specially prefer to use for this purpose (although
the method may be applied to others) is that first described, and consisting of a
single straight core electro-maguet each end of which acts on one of the two
opposed diaphragms which are clamped on to a central ring seating containing the
electro-magnet, and whose core is preferably polarised by a permanent magnet in
one of the forms described. We then prefer to place the low resistance circuit or
primary, on a coil in the centre of the length of the core of the electro-magnet,
(which core is preferably made of a bundle of iron wires or similar laminations),
and the high resistance or secondary circuit on two short coils occupying the outer
ends of the core, and which are thus immediately opposed to the diaphragms.
In consequence of the magnetic polarization of the core produced by the flow of
the battery current in the primary circuit, this form of telephone may also be used
without a permanent polarising magnet, but where such are used care must be
taken to connect the primary coils in such direction, that the battery current
magnetization increases, and not diminishes, that produced by the permanent
magnets.
:
Where such combined receiver and induction coil is used in conjunction with
the diaphragm contact described above for signalling purposes, we prefer to join
the make and break contact on the diaphragm (by means of a key capable of
being operated at will) in series with the battery and primary coil, instead of the
high resistance or secondary coil, while being used for signalling purposes,
keeping the secondary in the line circuit, as by so doing a much smaller battery
is enabled to more powerfully operate the receiver or receivers at the distant
station or stations.
Dated this 24th day of October 1894.
improvemens m песите гетерполоз, аци
thereon.
We,
ALFRED CHARLES BROWN, Electrician, of 129, Algernon Road, Lewisham,
in the County of Kent, and GEORGE RICHARD NEILSON, Secretary to Public
Company, of 50, Old Broad Street, in the City of London, do hereby declare

page_text: 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 :-
These improvements relate to the production of an electric telephone receiver
capable of giving a very clear and loud reproduction of articulate and other sounds
while retaining a small and compact form; to a means of signalling thereon (also
partly applicable to existing telephone systems); and a means of causing the
receiver coils to fulfil the functions of the separate induction coils heretofore used
in conjunction with the transmitters, at both ends of the line, so as to cut out the
waste resistance and self-induction of the secondaries of the induction coils, and so
increase the current energy available to operate the distant receivers.
We will fully describe our invention in reference to the accompanying drawings
in which
Fig. 1 is a section on line a-x of Fig. 2, which is a cross-section on line Z-Z
of Fig. 1.
Fig. 3 is a reduced view of steel magnet;
Fig. 4 is a cross-section of an alternative arrangement;
Fig. 5 a reduced view of bar magnet used in Fig. 4;
Figs. 6, 7, and 8 are vertical sections of modified constructions;
Fig. 9 is a section on line Y-Y of Fig. 8; and
Fig. 10 is a plan of an alternative arrangement of receiver and its connection.
To fulfil the above objects we construct our telephone receiver preferably with
two diaphragms A A, Fig. 1, opposed to each other having a ring or similar
seating B between them on to which they are clamped by two end pieces b b which
may be screwed over or into or otherwise affixed to the central ring seating B, and
have recesses turned out so as to clamp the diaphragms round near their edges but
leaving a shallow chamber C over the larger part of the surface of the diaphragms
on their outsides, which chambers are practically airtight.
The diaphragms are then actuated by an electro-magnet or electro-magnets M
placed between them and affixed to the central ring seating B, which seating also carries
on one side an ear piece F communicating with the inside air space contained between
the two diaphragms. If one electro-magnet is used it may consist of a single coil
and straight core m, each end or pole of which acts on one diaphragm. If more
than one coil is used however, care must be taken that they are joined in such way
that each diaphragm is attracted towards the centre or released away by the same
direction current as respectively attracts or releases the other diaphragm. We
then polarise the core of the electro-magnet M, when a single straight one is used
as described above, by placing round the outside of the coil or coils of the electro-
magnet a tube of steel S preferably slit down one side as at s, Fig. 3, and magnetised
as nearly to saturation as possible so that one of its flat ends which faces a
diaphragm is north-seeking and the other south-seeking, and the magnetic circuit is
then completed, less the small necessary air gaps, through the diaphragms
themselves and the central core of the electro-magnet, which together with the
diaphragms is thereby strongly polarised by induction.
The steel tubular magnet S may also if desired itself form the central case or
ring seating for the diaphragms. Or if a separate case be used, an equivalent of
the tubular magnet may of course be made by arranging a number of separate bar
magnets S¹, Figs. 4 and 5, round inside the case but outside of the coil of the
electro-magnet M, with their similar poles all at the same end, and so that they
together practically form a laminated tube round the electro-magnet. The
polarising magnets may also be bowed outwards in the middle to increase their
lengths, projecting if desired through the central casing. Or we may polarise the
core of the electro-magnet by connecting its central portion between the two
diaphragms to the pole of a steel magnet S which may either extend straight away
at right angles to the core and project through the central ring seating B so as to
form a handle H for the instrument as in Fig. 6, or may be curved away round the
outside of the coils but inside the casing as in Fig. 7 so as to get as great as possible
a length and have its other ends s¹ preferably but not necessarily thickened so as

page_text: to connect it more closely with both the diaphragms A A at some point near their
edges, two shorter coils M' M' being used in these instances, one placed on each
end of the cross core m, so as to be opposed one to each diaphragm, and joined in
circuit as heretofore described. Or we may use a horse-shoe magnet opposed to
each diaphragm, as shown in Figs. 8 and 9, in which case the polarising magnet
or magnets S may as before extend out at right angles through the case В so as to
form a handle H, or may be circular or approximately similarly curved, so as to
lie around the outside of the coils but inside the space contained within the central
ring seating B, or they may themselves form the ring seating, and with their poles
extended inside towards the cross cores m' m' and about midway between the
diaphragms by pole pieces so as to oppositely polarise each limb of the cross cores
which extend from thence towards the diaphragms, so as to form two horse-shoe
magnets one opposed to each diaphragm, four small coils M', M³, M³, M', being
then used and all joined in circuit so as to fulfil the above mentioned condition as
to attracting both diaphragms together.
In each of the above cases the object is to keep the polarising magnets, which
charge the cores of the electro-magnets, either within the space contained between
the two diaphragms and inside or else forming part of the substance of the central
ring seating, or casing, or else to arrange that the magnets shall form a convenient
central handle for the complete instrument.
The part of our invention relating to signalling consists in causing the receiver
(which for this purpose may be either as above described or any ordinary previously
used form) to emit a loud buzzing sound, capable of attracting attention from a
distance and useful for a variety of other signalling purposes, by one of the
following means. Where the instruments are used on "private lines," or circuits
which do not communicate with an exchange, we screw through or otherwise affix
to some part of the case of the receiver opposite to the outside (or side farthest
from the electro-magnet) of the diaphragm, (or one of the diaphragms, if the
receiver have more than one) a metal contact screw K, Fig. 1, taking care that
the body of same is by an ordinary means insulated from the diaphragm itself.
We then connect this contact screw K in series in circuit with the coils of the
receiver, the circuit being completed through the diaphragm of the instrument
with which the point of the said contact screw makes contact when properly
adjusted, the contact surfaces k k of both the screw and diaphragm being of course
properly platinised. When a direct battery or generator current is then passel
through such a receiver the diaphragm is vibrated electro-magnetically and so
produces a loud buzzing sound. If another receiver be joined in series or parallel
circuit also, the second receiver will likewise be caused to sound, and for this
purpose it is not necessary to include the contact of the second receiver in series
with the first but only the coils, so that the contact and coils of the first receiver
may be included in a local battery or generator circuit, while the extra current
from the coils of the first receiver are used to operate the second receiver or any
number of other receivers, which arrangement gives the maximum of sound with
the minimum current. This method of connecting is indicated in Fig. 1 wherein
E is the main lead from earth or return circuit passing through the coils M of the
receiver and continuing out through any other instruments that may be required
to line at E and ultimately to other (usually distant) receivers which are required
to be sounded. The local battery is represented by X, one pole of the battery
being connected through signalling button e to one side of the coils M of the
receiver; the other side of said coils is connected to the diaphragm A or one of
the diaphragms from which the local circuit is continued through the contact
screw K back to the other pole of the local battery.
We also prefer to load the central portion of the diaphragm of the receiver
carrying the contact with a heavier piece of iron as at K¹, Fig. 1, which greatly
increases the loudness of the buzzing sound and eases the adjustment without
appreciably affecting or decreasing the loudness and clearness of the articulation
of the receiver for vocal telephonic sounds...

page_text: For "exchange circuits," however, or lines communicating with a central station,
we prefer to produce the buzzing sound in the receivers at the subscribers' or out
stations, for signalling from the exchange or central station to the out stations (or
similar purposes), by means of a powerful induction coil placed at or in connection
with the exchange, and having a rapidly interrupted battery or generator current
passed continuously through its primary while the exchange is operating (or
capable of being switched on or off at will). The circuits at the exchange are then
so arranged (subject to the particular switch system then in use) that the operator's
signalling keys serve to connect one end of the secondary of the induction coil to
the subscribers' lines (the other end of the induction coil being to earth), instead
of connecting the battery or generator current heretofore used for actuating the
bells or other signals at the out stations, and thus by our invention we are able to
produce the call signal by a buzzing sound in the receiver at the subscriber's
station and to save the usual bell, switches and connections.
Or instead of an induction coil, an ordinary electro-magnet and make and break
may be used, kept going by a local current at the exchange, and the extra currents
from the coils of this electro-magnet put to the out-station lines by the operators'
signalling keys, instead of the currents from the secondary of the induction coil.
In order to cause & telephone receiver to act as its counterpart's induction coil
we may sometimes wind them with two different circuits, one having a low resistance
and being arranged to be connected in the local battery circuit together with the
transmitter when the instrument is in action, and the other having a high resistance
and being connected to line and to the distant receiver, so that the low resistance
circuit forms the primary, and the high resistance circuit the secondary (as in
ordinary induction coils,) as well as actuating the receiver's own diaphragm or
diaphragms. This arrangement is illustrated in Fig. 10 hereinafter described.
The two coils or circuits may be variously disposed on their respective cores, as
for instance wound one underneath the other in the ordinary way, but are better
wound as separate coils and placed upon different parts of the length of the same
core, so that while the primary or low resistance circuit can act inductively on the
secondary or high resistance circuit, the latter occupies the position of closer
proximity to the diaphragm or diaphragms, and is therefore more efficient in
vibrating it or them, in response to currents received from the line.
The form of receiver which we specially prefer to use for this purpose (although
the method may be applied to others) is that first described, and illustrated in
Fig. 10, and consisting of a single straight core electro-magnet M each end of which
acts on one of the two opposed diaphragms A. A. which are clamped on to a central
ring seating as at B, Fig. 1, containing the electro-magnet, and whose core m is
preferably polarised by a permanent magnet in one of the forms described. We
then prefer to place the low resistance circuit or primary P on a coil in the centre
of the length of the core m of the electro-magnet M (which core is preferably
made of a bundle of iron wires or similar laminations), and the high resistance or
secondary circuit P' on two short coils occupying the outer ends of the core,
and which are thus immediately opposed to the diaphragms.
In consequence of the magnetic polarization of the core produced by the flow of
the battery current in the primary circuit, this form of telephone may also be used
without a permanent polarising magnet, but where such are used care must be taken
to connect the primary coils in such direction that the battery current magnetization
increases, and not diminishes, that produced by the permanent magnets.
Where such combined receiver and induction coil is used in conjunction with the
diaphragm contact described above for signalling purposes, we prefer to join the
make and break contact on the diaphragm (by means of a key e capable of being
operated at will) in series with the battery X and primary coil P, instead of the
high resistance or secondary coil P, while being used for signalling purposes,
keeping the secondary in the line circuit, as by so doing a much smaller battery is
enabled to more powerfully operate the receiver or receivers at the distant station
or stations.

page_text: Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. In a telephone receiver the arrangement and combination of a central or
cylindrical casing or ring seating with ear piece and with two diaphragms both
adapted to be simultaneously vibrated in opposite directions to or from each other,
and polarised by magnets, substantially as above specified.
2. In a telephone receiver having two diaphragms clamped on to a cylindrical
seating, the use for polarising such diaphragms and cores of a split steel tube such
as S encircling the coils as above described, or for the same purpose of bar magnets.
such as S', or of horseshoe magnets S³, or of magnets arranged or adapted to operate
substantially as above described and illustrated.
3. The combination in a telephone receiver of a primary of an induction coil
connected in circuit with the transmitter and local battery, with the coil or coils
normally used for actuating the receiver, which is or are thereby caused to act also
as the secondary of the induction coil, for the purpose of eliminating the resistances
and impedances of the secondaries of the induction coils otherwise usually employed,
and thereby increasing the amount of current energy available for actuating the
receiver diaphragms at both ends of an ordinary telephone circuit, substantially as
above set forth.
4. The method of causing a telephone receiver to produce a loud buzzing sound
by providing a contact screw to make contact with its diaphragm or one of its
diaphragms if it have more than one, said contact screw and diaphragm being
joined in circuit with a battery and one of the coils of receiver as above described.
5. The method, apparatus, and electrical connections above described for calling
attention at a subscriber's station from an exchange or central station by sending
through the coils of the subscriber's out-station telephone receivers the currents
generated by an induction coil, or the extra currents from an electro-magnet, joined
in circuit in either case with a current generator and rapid make and break,
substantially as and for the purposes above set forth.
Dated this 23rd day of July 1895