IMPROVEMENTS IN TELEPHONE RECEIVERS
Year: 1881

page_text: LETTERS PATENT to Richard Theiler and Meinrad Theiler, both of 86, Canon-
bury Road, in the County of Middlesex, for an Invention of "IMPROVEMENTS
IN TELEPHONE RECEIVERS."
PROVISIONAL SPECIFICATION left by the said Richard Theiler and Meinrad
Theiler at the Office of the Commissioners of Patents on the 16th November
1881.
RICHARD THEILER and MEINRAD THEILER, both of 86, Canonbury Road, in the
County of Middlesex. IMPROVEMENTS IN TELEPHONE RECEIVERS."
"
This Invention has for its object improvements in telephone receivers.
In all previous systems of telephone receivers in which an electro magnet was
used the sonorous vibrations received were due either to the motion of an iron
diaphragm or armature placed close to the poles of the electro magnet, or in a form
of telephone, but little used to the longitudinal expansion and contraction of the
magnet itself while under the influence of a vibrating current.
Our Invention consists in the construction of electro magnetic telephone receivers
in which the armature is entirely dispensed with, and the lateral vibration of the
electro magnet is made use of.
For this purpose the electro magnet may be made of the usual U shape, and
may consist either of soft iron or of hardened steel permanently magnetised wound
with a suitable number of turns of insulated wire. This electro magnet is fixed in
such a manner that the vibrations of either one or of both its limbs is communi-
cated to a diaphragm or diaphragms.
We also employ two or more electro magnets in the same circuit, and utilise the
vibrations of both magnets in the manner described.
By attaching a light disc or discs to the vibrating limbs the diaphragm may be
dispensed with.
We sometimes damp the vibrations of the electro magnet to prevent their free
vibration.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Richard Theiler and Meinrad Theiler in the Great Seal Patent
Office on the 13th May 1882.
RICHARD THEILER and MEINRAD THEILER, of 86, Canonbury Road, Islington, in
the County of Middlesex. "IMPROVEMENTS IN TELEPHONE RECEIVERS."
This Invention has for its object improvements in telephone receivers.
In all previous systems of telephone receivers in which an electro magnet was
used the sonorous vibrations received were due either to the motion of an iron
diaphragm or armature placed close to the poles of the electro-magnet, or in a
form of telephone, but little used to the longitudinal expansion and contraction of
the magnet itself while under the influence of a vibratory current.
Our Invention consists in the construction of electro-magnetic telephone receivers
in which the armature is entirely dispensed with, and the lateral vibration of the
electro magnet is made use of.
For this purpose the electro-magnet may be made of the usual U shape, and
may consist either of soft iron or of hardened steel permanently magnetised wound
with a suitable number of turns of insulated wire. This electro magnet is fixed in
such a manner that the vibration of either one or of both its limbs is communi-
cated to a diaphragm or diaphragms.
We also employ two or more electro magnets in the same circuit, and utilise
the vibration of both magnets in the manner described.
By-attaching a light disc.or discs_to_the_vibrating_limbs_the_diaphragm.may_be
dispensed with.
We sometimes damp the vibrations of the electro magnet to prevent their free
vibration.
Fig. 1 represents one of our telephone receivers provided with two diaphragms
or sounding boards D, D, connected to the two limbs or cores of the U shaped
electro-magnet E by the short tongues c, c'. These tongues are firmly inserted in
the diaphragms and fixed to the magnet, as shown. The poles S, N, of the electro
magnet are brought very close together by being shaped as shown, and the middle
part of the magnet is firmly screwed to the case A, A, of the instrument. The
ends of the helix surrounding the magnet cores may be attached as usual to two
terminals, or soldered to a flexible conductor communicating with the other parts
of the telephone apparatus.
When a vibratory current is sent through the helix of the electro magnet the
extremities N, S, are rapidly attracted and repelled, and this vibratory motion of
the magnet cores being communicated to the diaphragms or sounding boards, the
latter are set in vibration of varying amplitude produced by a current of varying
strength, as in all other telephones.
Instead of making the electro-magnet of one continuous piece of iron, as repre-
sented in Fig. 1, we find it more practicable to make it of the form shown in
Fig. 2, where the electro magnet represented consists of the two limbs or cores e, e¹,
the sole piece b, and the pole extensions d, d', the whole being screwed together
and practically constituting one continuous piece of iron carrying the two
coils n, n'.
In Fig. 2 only one of the limbs or cores of the electro magnet is attached to the
diaphragm D, the other limb being held fixed by the screw h.
We sometimes hinge or pivot one of the magnet cores, or both of them, in the
sole-piece b, in which case the diaphragms or sounding boards can be made much
thicker than when the cores are rigidly fixed to the sole piece, because the
magnetic attraction of the poles S, N, has then only to overcome the resistance of
the diaphragm.

page_text: Instead of using a diaphragm we sometimes fix a stem f, Fig. 3, to one of the
cores of the electro magnet, and mount thereon a light disc G of vulcanite, wood,
ivory, gutta percha, or any other substance which is capable of vibrating.
When using this telephone receiver the said disc is pressed to the ear in such a
manner that its surface covers the aperture of the ear. To guide the correct
placement of the disc against the ear we sometimes make either the screw head
which holds the disc, or the central part of the disc itself, of such a shape that it
can be conveniently inserted in the ear.
When we use our telephone receivers on a line of some considerable distance we
prefer to magnetiso the electro magnet by a constant current from a local battery,
and to effect the variation of this constant magnetisation inductively, not directly.
Fig. 4 shows the mode of connecting the telephone receiver for this purpose.
The electro magnet E is not inserted in the line at all, but in the primary circuit
of an induction coil K, and connected with a local battery, as shown. The line is
connected to the secondary circuit of this induction coil.
This device possesses the advantage that the electro magnet can be powerfully
magnetised with very little battery power, no matter how long the line may be,
and that steel magnets are entirely dispensed with.
It is not necessary to have a separate battery for this purpose, as the microphone
battery may also be used for the telephone receiver.
The shape of the vibrating electro magnets herein described is immaterial, and
we may make them of a variety of forms not represented in the Drawing.
We claim as our Invention,―
First. The construction of a telephone receiver in which the lateral vibrations of
the limbs or cores of an electro magnet, or of several electro magnets, produced by
a vibratory current are made use of by being communicated to a diaphragm or
diaphragms, or to a sounding board or sounding boards.
Second. The construction of a telephone receiver in which the lateral vibrations
of one of the cores of an electro magnet are communicated to a loose or fixed disc
made of any substance which is capable of vibrating, as herein described.
Third. The construction of telephone receivers, substantially the same as
represented by Fig. 1, 2, and 3 of our Drawing, and as herein described.
Fourth. The mode of magnetising the telephone receivers by a local battery,
and varying this constant magnetisation inductively, as herein described and shown
by Fig. 4.
In witness whereof, we, the said Richard Theiler and Meinrad Theiler, have
hereunto set our hands and seals, this Thirteenth day of May, in the year
RICHARD THEILER. (L.S.)
MEINRAD THEILER. (L.S.)