IMPROVEMENTS IN TELEPHONIC APPARATUS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by George Lee Anders at the Office of
the Commissioners of Patents on the 28th August 1882.
GEORGE LEE ANDERS, of Queen Victoria Street, in the City of London,
"Electrician, "IMPROVEMENTS IN TELEPHONIC APPARATUS."
"
My invention relates to that class of telephones wherein a loose contact through
which the current passes serves both for the receiving and transmitting instru-
ments, but the instruments which I thus use for both purposes interchangeably
may be used solely as transmitting instruments in connection with any ordinary
form of electro-telephonic receiver, or may serve as receivers in connection with
any ordinary form of transmitter, and I may modify the instrument used as a
transmitter to make it especially convenient for speaking into and the one used as
a receiver to make it convenient for listening without in either case departing from
the spirit of my invention as exemplified in the interchangeable types of .my
instruments.
•
I find after investigation of a large number of materials for use as the contact
points or surfaces of such transmitting and receiving instruments that tellurium is,
by reason of certain qualities which I have discovered it to possess, peculiarly
adapted for the purpose of my invention. This substance has among other advan-
tages the property of very rapidly diminishing its resistance to the passage of an
electric current when its temperature is raised even slightly, a property possessed
to the same degree by no other substance which is an equally good conductor of
electricity. By virtue of this property tellurium has the advantage for use in
forming the contact surfaces of telephone transmitters that an increase of pressure
upon the contacts by diminishing the resistance of the circuit and allowing a
stronger current to flow thereby causes the material of the contacts to be heated by
the current which as above explained has the effect of still further diminishing the
resistance. Again when the pressure is reduced the resistance being increased the
current diminishes in strength and the material of the contacts is allowed to cool,
thereby still further increasing the resistance to the current. Thus the variations
in the resistance of the circuit due to both increase and. diminution of pressure
upon the contact are aided by the peculiar property of the tellurium as above
explained. Moreover tellurium has peculiarities of molecular structure which

page_text: distinguish it from all other good conductors of electricity as a material for
transmitter contacts in that it is capable of such use without giving trouble from
fusion and sticking together of the surfaces in contact while at the same time giving
rise to sufficient variations of surface resistance under the influence of varying
pressure notwithstanding an initial pressure sufficient to prevent too easy breaking
of the contact.
The property above specified as specially fitting tellurium for the contact surfaces
of transmitters also makes it peculiarly valuable for receiving contacts. The action
of a loose contact as a receiving telephone is due to a varying heating and conse-
quently varying expansion of the material of the contact surfaces under the
influence of the varying current produced by the action of the transmitter. Now
tellurium in consequence of diminishing its resistance when heated by the passage
of the current reinforces the action of the transmitter. Again when the heat of
the contacts is diminished by a decrease of current the resistance of the receiving
instrument also increases which has the effect of still further diminishing the
current. Furthermore the same peculiarities of molecular constitution which have
been mentioned as causing the transmitter contact to work freely and efficiently
have a similar effect and value in the case of the receiving contact.
In practising this invention I introduce my improved telephonic regulator between
the terminals or interrupted portions of the circuit in the proper relative position
with regard to the diaphragm disc or plate or other device to be acted on by the
sound waves. The said regulator is in some instances formed of two surfaces of
tellurium one fixed on the diaphragm or disc and the other arranged in contact
therewith; or this material may be used in a powdered or granulated condition
placed between discs or plates or in a recess or chamber in such a manner as to
form connection between the two terminals or ends of the otherwise interrupted or
open circuit.
In some cases I construct a transmitter with a disc formed of two plates each of
which forms one terminal of the circuit, the said plates being connected by
vulcanite or any suitable insulating material and I arrange this disc at the bottom
of a recess or chamber which I fill or partly fill with tellurium in a granulated or
other condition. Or I use blocks or pieces of tellurium cut moulded or pressed into
the required shape and arrange the same in combination with each other or arrange
a block or piece of tellurium with a point or projection on a diaphragm or disc or
I arrange the regulator in any manner best suited to the kind or character of the
telephonic instrument to which it is applied. The blocks or pieces of the regulator
may be formed of solid tellurium or of pieces of other material coated with the
same.