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THEILER'S TELEPHONE RECEIVER.


This telephone receiver differs from its predecessors in dispensing with
an armature, the lateral vibration of the electro-magnet itself being
utilized. In previous systems in which an electro-magnet is used, the
sonorous vibrations are due either to the motion of an iron diaphragm
or armature placed close to the poles of the electro-magnet, or to the
expansion and contraction of the magnet itself. In Theiler's telephone
the electro-magnet may be of the usual U-shape, and may consist either
of soft iron or of hardened steel permanently magnetized, 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 communicated to a diaphragm or diaphragms The patentees also employ
two or more electro-magnets in the same circuit, and utilize the
vibration of both magnets in the manner described. By attaching a light
disk or disks to the vibrating limbs, the diaphragm may be dispensed
with. Fig. 1 represents one of the telephone receivers provided with two
diaphragms or sounding boards, connected to the two limbs or cores of
the U-shaped electro-magnet by short tongues. These tongues are firmly
inserted in the diaphragms and fixed to the magnet, as shown. The poles
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
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