Telegraph, Wheatstone, A. B. C.
A magneto-electric telegraph of the dial system. An alternating current
magneto-generator is turned by hand and by depressing keys its current
is admitted to or cut off from the line and receiver's instrument. The
message is received by a dial instrument working by the escapement
motion described under Telegraph, Dial.
Telegraph, Writing.
A telegraph in which the message is received in written characters. The
transmitter includes a stylus which is held in the hand and whose point
bears against the upper end of a vertical rod. The rod is susceptible of
oscillation in all directions, having at its base a spring support
equivalent to a universal joint.
The stylus is moved about in the shape of letters. As it does this it
throws a series of resistances in and out of the circuit.
At the receiving end of the line the instrument for recording the
message includes two electro-magnets with their cores at right angles to
each other and their faces near together at the point of the angle. An
armature is supported between the faces and through it a vertical rod
carried by a spring at its bottom rises. These magnets receive current
proportional to the resistances cut in and out by the motions of the
other rod at the transmitting end of the line. These resistances are
arranged in two series at right angles to each other, one for each
magnet. Thus the movements of the transmitting stylus and rod are
repeated by the end of the rod in the receiving instrument. A species of
pen is carried at the end of the rod of the receiving instrument, which
marks the letters upon a riband of paper which is fed beneath it.
Telemanometer. Electric.
A pressure gauge with electric attachment for indicating or recording
its indications at a distance.
It is applicable to steam boilers, so as to give the steam pressure in
any desired place.
Telemeter, Electric.
An apparatus for electrically indicating or recording at a distance the
indications of any instrument such as a pressure gauge, barometer or
thermometer, or for similar work. The telemanometer applied to a boiler
comes into this class of instrument.
Telephotography.
The transmission of pictures by the electric current, the requisite
changes in the current being effected by the action of light upon
selenium. The picture is projected by a magic lantern. Its projection is
traversed by a selenium resistance through which the current passes.
This is moved systematically over its entire area, thus constituting the
transmitter, and synchronously with the motion of the selenium a contact
point at the other end of the line moves systematically over a sheet of
chemically prepared paper. The paper, which may be saturated with a
solution of potassium ferrocyanide and ammonium nitrate, is stained by
the passage of the current, and by the variation in intensity of
staining, which variation is due to variations in the current, produced
by the effects of the light upon the selenium, the picture is
reproduced.