SIGNALS CONVEY INTELLIGENCE
A simple electrical telegraph circuit.
Conveying Intelligence over the Electrical Telegraph
. This model of a
simple telegraph circuit consists of a copper wire loop with a buzzer inserted at the
distant end where the wire pair loops around. At the near end, which we may call the
transmitting end, there is an electrical switch, which we will call a key. The key consists of
two electrical contacts, which, when pressed together, make contact, thereby closing the
circuit and permitting current to flow. The key is spring-loaded, which keeps it normally
in the open position (no current flow).
To convey intelligence, the written word, a code was developed by Morse, consisting
of three elements: a dot, where the key was held down for a very short period of time; a
dash, where the key was held down for a longer period of time; and a space, where the
key was left in the "up" position and no current flowed. By adjusting the period of time of
spaces, the receiving operator could discern the separation of characters
(A, B, C, . . . , Z)
and separation of words, where the space interval was longer. Table 2.1 shows the land-
line and international versions of the Morse code. By land-line, we mean a code used to
communicate over land by means of wire conductors. The international Morse code was
developed somewhat later and was used by radio.
Two Versions of the Morse Code
Column A: the American Morse Code; Column B: the International Morse Code
To convey intelligence, the written word, a code was developed by Morse, consisting of three elements: a dot, where the key was held down for a very short period of time; Table 2.1 Two Versions of the Morse Code Column A: the American Morse Code;