Telegraph, Hughes'.
A printing telegraph in very extensive use in continental Europe. Its
general features are as follows:
The instruments at each end of the line are identical. Each includes a
keyboard like a piano manual, with a key for each letter or character.
On each machine is a type wheel, which has the characters engraved in
relief upon its face. With the wheel a "chariot" as it is termed also
rotates. The type wheels at both stations are synchronized. When a key
is depressed, a pin is thrown up which arrests the chariot, and sends a
current to the distant station. This current causes a riband of paper to
be pressed up against the face of both type wheels so as to receive the
imprint of the character corresponding to the key. The faces of the
wheels are inked by an inking roller.
Fig. 317. ELECTRO-MAGNET OF HUGHES' PRINTING TELEGRAPH.
The most characteristic feature is the fact that the current sent by
depressing a key does not attract an armature, but releases one, which
is then pulled back by a spring. The armature is restored to its
position by the mechanical operation of the instrument. The magnet used
is a polarized electro-magnet. Coils are carried on the ends of a strong
powerful magnet. The coils are so connected that a current sent through
them by depressing a key is in opposition to the magnetism of the
permanent magnet so that it tends to release the armature, and in
practice does so. This release permits the printing mechanism to act.
The latter is driven by a descending weight, so that very slight
electric currents can actuate the instruments.
Synonym--Hughes' Type Printer.
Telegraphic Code.
(a) The telegraphic alphabet, as of the Morse System. (See Alphabet,
Telegraphic.)
(b) A code for use in transmitting messages either secretly, or
comprising several words or short sentences in one word, in order to
economize in transmission. Such codes are extensively used in commercial
cable messages.