Improvements in Telephones.
Year: 1891

page_text: Date of Application, 1st June, 1891
Complete Specification Left, 29th Feb., 1892-Accepted, 2nd Apr.. 1892
PROVISIONAL SPECIFICATION.
[Communicated from abroad by Messrs. SIEMENS & HALSKE, of Berlin, in the
German Empire, Electrical Engineers.]
Improvements in Telephones.
We, SIEMENS BROTHERS & Co. LIMITED of 12 Queen Anne's Gate,
Westminster in the County of Middlesex, Electrical Engineers, do hereby
declare the nature of this invention to be as follows:-
Telephone receivers to be effective, require the combination of great distinctness
of sound in conjunction with freedom from the sounds produced by the vibrations.
of the instrument itself, and of great lightness for the ready handling thereof.
These two requirements have not heretofore been combined. Telephones that
effectually transmitted the sound of speech without interference of local sounds
and which could be used without microphones, could not be constructed heretofore
without being comparatively heavy.
The present invention relates to an improved construction of telephones whereby
their weight is reduced to about one half that of former types without in any way
sacrificing the requisite clearness and purity of the speech.
This is effected mainly by mounting the iron membrane on a shallow box or cup
shaped casing of thin brass so as to form as it were the lid to the box. The short
elbow shaped flat electro magnet cores are fixed on a flat annular steel magnet,
which is either so magnetised as to have two diametrically opposite poles, or
which is constructed of two semicircular magnets placed with their poles opposite
each other. This permanent magnet is attached to the bottom of the box with
the intervention of a disc or layer of non elastic material such as vulcanite,
celluloid, soft lead etc. which prevents the transmission of sound vibrations from
the box and the magnet, and which is so fixed as to determine the exact position
of the poles of the electromagnet relatively to the membrane.
By this means the vibrations of the parts of the instrument are prevented, even
with the loudest transmitted sounds.
In constructing the said instrument, the cylindrical box or cup shaped case has a
circular flange to which is fixed the membrane and the ear piece by means of
screws and an external annular metal washer. The elbow shaped cores of the
electro magnet are fixed by their one limb to the two semicircular steel magnets by
screws, the other limbs which carry the windings, projecting towards the membrane;
the steel magnets are secured to the bottom of the box by means of other screws
with the interposition of the layer of non elastic material, thus securing the box
and the system of permanent and electro magnets rigidly together.
The, case is, in its turn, secured to the button-shaped solid handle of the
instrument at the back, by means of screws passing through the layer of non elastic
material and the bottom of the box. The windings of fine wire on the pole pieces
of the electromagnets are secured to terminals on an insulating piece fixed to the
face of the ring-shaped magnet, to which terminals are also secured the wire leads
of the circuit, passing through a side orifice in the casing. A metal loop for the
suspension of the instrument is secured by a screw to the side of the case opposite
that at which the leads enter.
According to another modification, instead of making the handle as a solid
button at the back of the case, we make it of a flat tubular shape, secured at the
side of the case, with the wire leads passing up through the same. The tubular
handle is preferably secured by means of a forked piece to the annular permanent.

page_text: magnet of the instrument, which forked piece then carries the insulated pinching
screws for securing the leads and the ends of the electromagnet winding.
Dated this 1st day of June 1891.
ABEL & IMRAY,
Agents for the Applicants.
Improvements in Telephones.
We, SIEMENS BROTHERS & Co. LIMITED of 12 Queen Anne's Gate,
Westminster in the County of Middlesex, Electrical 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:-
Telephone receivers to be effective, require the combination of great distinctness
of sound in conjunction with freedom from the sounds produced by the vibrations
of the instrument itself, and of great lightness for the ready handling thereof.
These two requirements have not heretofore been combined.
Telephones that effectually transmitted the sound of speech without interference
of local sounds and which could be used without microphones, could not be con-
structed heretofore without being comparatively heavy.
The present invention relates to an improved construction of telephones whereby
their weight is reduced to about one half that of former types without in any way
sacrificing the requisite clearness and purity of the speech.
The
This is effected mainly by mounting the iron membrane on a shallow box or
cup-shaped casing of thin brass so as to form as it were the lid to the box.
short elbow shaped flat electro maguet cores are fixed on a flat annular steel
magnet, which is either so magnetised as to have two diametrically opposite poles,
or which is constructed of two semicircular magnets placed with their poles
opposite each other. This permanent magnet is attached to the bottom of the box
with the intervention of a disc or layer of non-elastic material such as vulcanite,
celluloid, soft lead etc. which prevents the transmission of sound-vibrations from the
box and the magnet, and which is so fixed as to determine the exact position of the
poles of the electromagnet relatively to the membrane.
By this means the vibrations of the parts of the instrument are prevented, even
with the loudest transmitted sounds.
On the accompanying drawing is shewn the construction of a telephone according
to the present invention.
Fig. 1 shews a front view of the same with the membrane M and car piece S
removed. Fig. 2 shews a section, while Figs. 3, 4, 5 and 6 shew detached details.
Figs. 7, 8 and 9 shew a modified construction.
The cup shaped metal case D, stiffened by a metal ring R', soldered to it, carries
the membrane M, fixed thereto by means of the car piece S and the ring R², the
electro magnet system being fixed to the bottom of the cup.
The steel magnet consists of a flat ring which is magnetised in such a way that
two diametrically opposite parts thereof form strong opposite poles on which are
fixed the elbow shaped soft iron pole pieces " P2, so as to form practically one
therewith. It is preferred to divide the ring, so as to constitute the permanent
magnet by means of two half rings H H of hard steel, one of which is shewn
separate at Fig. 5. The poles of same name of these half rings are placed closely
opposite each other and carry the elbow shaped pole pieces P of soft iron on
which are mounted bobbins that receive the windings of fine electro magnet wire,
the ends of which are connected to two binding screws k¹k that are fixed on the
insulating plate A', as shown detached in section at Fig. 4, and which is fixed
directly upon the magnet H2 by means of screws. The fixed electromagnet
system formed by the soft iron pole pieces P1 P2 and the hard steel half-ring
magnets H H and the cup shaped metal case with the membrane fixed thereto,

page_text: are firmly secured together by means of screws S' S² with the interposition of an
intermediate disc Z which is formed of a substance such as ebonite, celluloid, soft
lead, or other material that is a bad sound transmitter, and which prevents the
transmission of the vibrations to the casing and magnets, and thus has the effect of
preventing the production of detrimental subsidiary sounds when the membrane is
made to vibrate under the action of the electromagnet. By this construction an
unimpaired loud transmission of speech is effected even when very strong vibrations
are produced by the strong action of a microphone. The disc Z also serves to
accurately determine the correct distance of the electromagnet poles from the
membrane.
It is to be observed that the electro maguet system forms practically one with the
insulating piece A' so that on loosening the screws S₁S these parts can be readily
removed from the casing, together with the flexible wire leads attached thereto by
the screws. The loop o serves for suspending the telephone while the
handle G serves for holding the same.
!
In the modified construction shewn in Figs. 7, 8 and 9, a lateral handle is formed
by a flat tube F which is fixed by a curved piece to the steel half ring H by
means of screws, the insulating piece A which carries the binding screws k¹³
being secured to the piece g by screws »³.
The wire leads pass through the end piece of the handle F, and up through the
latter to the binding screws as shewn. The other parts of the telephone are of the
same construction as previously described.
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 telephones, the combination of a polarised electro-magnet system with
circular flat steel magnet with a shallow cup shaped metal case, to the bottom of
which such electromagnet system is secured, while the iron membrane is made to
form the cover of the casing, substantially as described.
2. In a telephone such as is referred to in the preceding claim, effecting the
separation of the steel magnet of the electromagnet system from the bottom of the
cup shaped casing by means of a disc of material such as ebonite, soft lead, and
the like, that is a bad transmitter of sound, in order to prevent or reduce the
vibrations of the casing and electromagnet, and at the same time to insure the
maintenance of the proper distance between the magnet poles and the membrane,
substantially as described.
3. In a telephone such as is referred to in the preceding claims, fixing the
insulating piece carrying the wire leads, or the lateral handle with the wire leads,.
on the steel magnets substantially as described.
Dated this 29th day of February 1892.
ABEL & IMKAI,
Agents for the Applicants..