As for chatting, all the intercoms are full-duplex, allowing for normal back-and-forth conversation. On the other hand, the bike-to-bike communicators are almost all of the "simplex" variety, where only one person can speak at a time. Most systems feature VOX (Voice Operated eXchange) so that the intercom is silent unless someone is speaking. Many systems also include a PTT (Push-To-Talk) button, usually for bike-to-bike communication, but sometimes for the intercom, too. This prevents the microphone from transmitting until someone presses the PTT button.