Telephone, Capillary.
A telephone utilizing electro-capillarity for the production of
telephonic effects. The following describes the invention of Antoine
Breguet.
The point of a glass tube, drawn out at its lower end to a capillary
opening dips vertically into a vessel. This vessel is partly filled with
mercury, over which is a layer of dilute sulphuric acid. The end of the
immersed tube dips into the acid, but does not reach the mercury. One
line contact is with mercury in the tube, the other with the mercury in
the vessel. The arrangement of tube and vessel is duplicated, giving one
set for each end of the line. On introducing a battery in the circuit
the level of the mercury is affected by electro-capillarity. The tubes
are closed by plates or diaphragms at their tops, so as to enclose a
column of air. It is evident that the pressure of this air will depend
upon the level of the mercury in the tube, and this depends on the
electro-motive force. On speaking against the diaphragm the sound waves
affect the air pressure, and consequently the level, enough to cause
potential differences which reproduce the sound in the other instrument.
Fig. 327. BREGURT'S CAPILLARY TELEPHONE.
Telephone, Carbon.
A telephone transmitter based on the use of carbon as a material whose
resistance is varied by the degree of pressure brought to bear upon it.
Undoubtedly the surface contact between the carbon and the other
conducting material has much to do with the action. Many carbon
telephones have been invented. Under Telephone the Blake transmitter is
described, which is a carbon telephone transmitter. The Edison carbon
transmitter is shown in section in the cut. E is the mouth piece and D
the diaphragm. I is a carbon disc with adjusting screw V. A platinum
plate B B, with ivory button b, is attached to the upper surface of the
carbon disc. C C is an insulating ring. The wire connections shown bring
the disc into circuit. It is connected like a Blake transmitter. It is
now but little used.
Fig. 328. SECTION OF EDISON CARBON TRANSMITTER.