TELEGRAPHIC APPARATUS. 
241 
so as to produce this interruption at the right instant, and 
cause dots or dashes to appear as may be required. 
We know how the perforated strip is carried forward. Two 
rods m and s are fixed at the ends of the levers A and b, which 
are themselves connected with the frame of the apparatus, so 
as to admit of their turning ; but they are kept in position by 
the springs s and s'. The rods jvi and s either pass through 
the perforations in the strip of paper, or are stopped in their 
upward movement if a perforation is not opposite to them. 
In fig. 172, we see the rod passed through one of the perfora¬ 
tions. r is a rocking lever of ebonite, in which are fixed two 
metal studs 1 and 2 ; this lever is kept in a constant state of 
regular oscillation by the wheelwork of the apparatus. These 
studs are in contact with arms of the levers A and b, which 
thus are made to oscillate in unison with r. At the lower part 
of the lever a is fixed a rod H, and a smaller one h' is attached 
to the upper part of b. The ends of these rods move freely 
through projections from the divided disc d. The collars K 
and k' by pushing p and p' make the disc oscillate in perfect 
accord with r. The lever c is provided with a screw, which, 
when the disc is in the middle of its oscillatory movement, abuts 
against a small piece of ebonite fixed in z, which prevents the 
battery being thrown into short circuit. The little roller E 
completes the part begun by k and k', and keeps the disc in its 
