The telegraph key is shown in the sketch below. (Fig. 6.)

[Illustration: Fig. 6]

This instrument is usually made of brass, except that upon the handle

there is the little knob which is of hard rubber. The handle, or lever,

moves down when this knob is pressed, and a little spring beneath

pushes it up again when let go. You will see a second smaller knob, the

use of which we will explain later.