The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

394 THE HOUSE PRINTING TELEGRAPH.
revolve with it by a friction contrivance, consisting of a brass
flange fastened permanently to the revolving shaft; the face
of the flange and the inner face of the circuit wheel are in
contact with a piece of cloth or leather interposed, moistened
with oil; the friction is regulated by a spring pressing against
the end of the revolving shaft c.
The object of this friction apparatus is to allow the shaft to
revolve while the cylinder can be arrested.
On the right end of the cylinder is fixed the brass wheel E,
fig. 3, four or five inches in diameter, called the circuit wheel,
or break; the outer edge of it is divided into 28 equal spaces,
each alternate space being cut away to the depth of one fourth
of an inch, leaving fourteen teeth or segments, and fourteen
spaces, Fig. 3, E; the revolving shaft and cylinder form part
of the electric circuit; one point of the connection being where
the shaft rests on the frame, the other through a spring F,
having connection with the other end of the circuit, pressing
on the periphery of the break-wheel E, fig. 3; G, the other
part of the circuit, coming from the axial magnet to the
frame A; when the shaft, cylinder, and circuit wheel revolve,
the spring will alternately strike a tooth and pass into an
open space; in the former case, the circuit is closed, in the
latter it is broken.
For the purpose of arresting the motion of the circuit wheel
and cylinder, the latter has two spiral lines of teeth n, fig. 3,
extending along its opposite sides, having fourteen in each line,
making 28, one for each tooth, and one for each space on the
circuit wheel; the cylinder extends the whole width of the
key-board above it; the latter is like that of a pianoforte, containing twenty-eight keys that correspond with the twentyeight projections on the cylinder, and have marked on them in
order, the alphabet, a dot, and dash, fig. 1; they are kept in
a horizontal position by springs; there is a cam or stop fixed
to the under surface of each key; directly over one of the
projections on the cylinder; these stops do not meet the teeth
unless the key is pressed down, which being done the motion
of the cylinder is stopped by their contact; by making the
circuit wheel revolve, the circuit is rapidly broken and closed,
which continues until a key is depressed; that key being
released, the revolution continues until the depression of
another key, and so on; the depression of a key either keeps
the circuit broken or closed; as it may happen to be at the
time, so that the operator does not break and close the circuit,
but merely keeps it stationary for a moment; from one to
twenty-eight openings and closings of the circuit take place