(Push-To-Talk)

PTT is a two-way communication service that works like a "walkie talkie".

A normal cell phone call is full-duplex, meaning both parties can hear each other at the same time. PTT is half-duplex, meaning communication can only travel in one direction at any given moment; only one person can be heard at a time.

To control which person can speak and be heard, PTT requires the person speaking to push a button while talking and then release it when they are done (hence the term Push To Talk.) The listener then presses their button to respond.

Most PTT systems allow group calling, meaning one person can speak to everyone in their assigned or current group at once, just by pressing a PTT key.

Some new PTT systems introduced in 2003 and later use VoIP technology to provide PTT service digitally over 3G data networks.