23B 
THE TELEGRAPH 
prolongation of the latter, and a dot by itself may fail to appear 
at all. 
The Morse signals can be reproduced by means of currents 
of uniform duration, by using a polarized armature so adjusted 
that it remains in the same position, after the contact is broken 
until an opposite current be sent; that is to say, so arranged 
that it works only by the effects of the currents. In. this system 
the dot is produced by a very short positive current, 
immediately followed by an equally short negative current; 
whilst the dash is produced by a very short positive current 
followed by a pause to allow the inking wheel to make a stroke, 
and then a negative current to detach the armature from the 
electro-magnet. 
By sending into the line very feeble currents during those 
intervals of time when, in the older system, it used to be left 
