TheCodeBreakers
and punctuation marks, shift back down to letters, return type-carriage
to left side of paper, feed paper up a line, and idle). Through an electrical
arrangement involving rotating commutators, the proper sequence of
pulses is sent out when a character's key is struck on the keyboard. For
example, a is mark mark space space space, i is space mark mark space
space and the figure shift is mark mark space mark mark. At the
receiving end, the incoming pulses energize electromagnets that, in
combination, select the proper character and print it. In the punched
paper tape which is frequently used to run teletypewriters, marks are
represented by holes and spaces by leaving the tape intact. To read the
tape, metal fingers push through the holes to make contact and thereby
send pulses; where there is a space, the paper keeps the fingers from
completing the circuit.
Vernam suggested punching a tape of key characters and
annaabi.ee 
