[ARC5] Keying Approach

[Jim Haynes]

A more plausible reason, to me, is that you might have more than one mike
plugged into the same radio.  So you want only the one that is intended
to key the transmitter to be connected to it.  Any others would just
increase the noise and reduce the signal from the intended mic.

Consider for example the BC-366 jack box. 
(COMP-LIAISON-COMMAND-INTER-CALL)  Several crew members might have the
rotary switchs set to the same position, but you only want one mike at
a time connected to the radio.

jhhaynes at earthlink dot net