The Sun.
London, England, 1863-09-19 00:00:00

The Hughes' Printing Telegraph,

The Hughes' Printing Telegraph requires but one
electrical wave for each letter which has to be trans-
mitted, whereas Morse's printer, Wheatstone's
needle, Bain's chemical, and the dial, or step-by-
step letter-printing telegraphic instrument, depend
either upon the number and duration of different
signals to produce the letter intended, or upon a
certain number of signals, each requiring an electric
wave to produce only one letter. For the Morse an
average of four waves is required for each letter,
and the dial requires seven. The chief mechanical
feature of this machine is the causing the almost
mathematically synchronous and continuous revolu-
tion of two type-wheels, one at the transmitting
the other at the distant receiving or recording sta-
tion, and causing
any little difference that may acci-
dentally occur to be corrected by the machine itself ;
first, at the commencement of work ; secondly, on
the printing of each letter as a message proceeds ;
so that when any given letter--for instance, A—is
lowermost at one station, it is also lowermost at the
other. By simple mechanical arrangements a cur-
rent can be transmitted when any required letter at
the sending station is in this position. This current
instantly, by detaching an armature, allows a ham-
mer to strike a slip
of paper against the correspond-
ing letter of the type-
wheel at the receiving station,
and so prints the letter without stopping the type-
wheel. It will be observed that exact synchronism
between the two type-wheels is absolutely neces-
sary. Approximate synchronism is obtained by the
adjustment of two vibrating springs in unison ; and
perfect synchronism is obtained by a small correc-
tion, produced, as each letter is printed, by the very
act of printing. The type-wheel is then either
hastened or retarded a little, as may be required, to
bring the letter truly opposite the printing
pad. The
test of this is, simply repeating the same signal
(suppose that of the repeat) several times at equal
intervals. The means by which the machine cor- 1
recta itself at each letter, or at the commencement
of work, is by means of a correcting cam—a solid
wedge, pushed down into a similar hollow wedge—
one on the driving part, the other on the arbour of
the wheel. The paper to be printed on is coiled on
a reel, and is drawn forward by the machine, and
pressed up against the letter to be printed by the
electric wave that brings the required letter or num-
ber to its place at the under side of the revolving
wheel. The mechanical motions are produced by
the force of a weight. as it descends acting upon a
train of wheels; a small bell rings when this weight
is nearly run down, and the assistant winds it np
by simply pressing his foot on a treadle. There are
28 keys, like the keys of a piano, each correspond-
ing to a letter or mark, as, say, a full stop, or to a
number, at pleasure. These admit of 56 variations,
so that the possibility of varying signals is nearly
unlimited. When one of the keys corresponding to
a letter is depressed, this brings a detent in contact
with a pin corresponding to that letter on the cir-
cumference of the uniformly revolving type-wheel,
stops it, and at the same time sends an electric wave
to the distant station, which, by an electro-magnet
detaching a similar detent, stops the same letter for
the instant, and by a revolving cam brought up
presses the paper against the type, the impression
of which is thus taken at the distant station ; the
rising of the detent by the key rising to its place
; simultaneously stops the electric current, and each
wheel again starts into motion at the same letter,
as they had each been stopped exactly at the same
letter, and so letter after letter is printed nearly as
fast as the keys of a pianoforte can be moved.
It was also pointed out that the instrument might
1 be used as a chromoscope ; and tables showing its
application to the measurement of retardation in
submarine cables were contained in the report.