Push-to-talk (PTT), also known as Press-to-Transmit, is a method of conversing on half-duplex communication lines, including two-way radio, using a momentary button to switch from voice reception mode to transmit mode.
Conventional two-way radios
For commercial, family and amateur two-way radios, PTT is a button that is pressed when needing to transmit with the radio on the tuned frequency or channel. While the PTT button remains unpressed (or unkeyed), any radio traffic that is received on the selected channel or frequency is heard through the radio's speaker. Unless the radio supports full-duplex operation, received audio is usually muted while the PTT button is pressed. Simultaneous full-duplex transmission and reception on a radio is generally not supported unless either the transmit and receive frequencies have significant separation between the two frequencies, or two different antennas are used with enough distance between them, or a cavity filter is used, due to an effect known as desensing which cancels out received transmissions.
More recently, the PTT concept has been adopted by cellphone carriers as a way to instantaneously send transmissions to other users on the system, emulating walkie-talkie communications on a mobile phone network.
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