PTT stands for Push-to-talk or Press-to-transmit (depending on
where you are when you ask). When using a communication system
that is half duplex (that is, when one party is sending all
others must receive) it serves to manage traffic. PTT originated
with voice radio and survives into the digital communications
era. In a voice communications system where more than one user
shares a transmit frequency or other medium, the transmitters
must by default be turned off to prevent interference. When a
user is ready to broadcast, they activate a momentary switch
which turns on their transmitter, send their message, and
release the switch. In most radio sets, this switch is a button
of some type which is, you guessed it, pressed to talk.
Typically, if the receiver is on the same frequency as the
transmitter, the receiver is disabled while PTT is active. Some
common uses of PTT include aviation radio, CB radio, walkie-
talkies and cell phones with PTT features. Those folks yelling
at their cell phones on the bus with th