The PTT button refers to the Push-To-Talk button used for the transmission of voice messages over the radio frequency. When the PTT button is pressed, the pilot's microphone becomes active, allowing them to speak and transmit their voice to the ATC or other aircraft tuned to the same frequency. Once the PTT button is released, the microphone stops transmitting, and the pilot is able to listen to incoming communications from ATC or other aircraft.

An irritating and potentially dangerous situation in radiotelephony is a “stuck” microphone button. Operators should always ensure that the button is released after a transmission and the microphone placed in an appropriate place ensuring that it will not inadvertently be switched on. Should your microphone button be stuck in the "transmit" position, your radio will keep transmitting permanently, and since VHF communications are not telephone communications, nobody else will be able to talk on that particular frequency, although they will hear everything you say.