With this mobile communications service, which is comparable to walkie-talkie, a subscriber can establish a group call with several people by pressing a PTT key on the cell phone. Since the transmission is in half- duplex, only one subscriber can talk at a time while the others receive. If several participants press the PTT key to use the voice channel, then the one who pressed first occupies the transmission channel.
The push-to-talk method has been standardized by the Open Mobile Alliance( OMA) and is implemented by various network operators and cell phone manufacturers. It is a low-cost alternative to trunked and private mobile radio. Push-to-Talk is also available as an IP-based voice service for General Packet Radio Service( GPRS) as Push-to-Talk over Cellular( PoC) and also for WLANs as Push-to-Talk over WiFi.