# PTT

AI-generated

Push to talk:
switching the radio into transmit before sending and back afterwards.
It can be done with a serial port’s RTS or DTR line,
a GPIO pin,
the GPIO of a [CM108](../cm108/index.html.md) audio adapter,
or a CAT command through Hamlib.
Its counterpart is DCD, data carrier detect,
which says the channel is busy so a transmission should wait.

## References

* [Hamlib](https://hamlib.github.io/)
* [Push-to-talk on Wikipedia](https://en.wikipedia.org/wiki/Push-to-talk)