Iridium Extreme Push to Talk (PTT) HandsetPowered by the worlds furthest reaching network, the Iridium Extreme PTT is engineered to support high intensity users with the worlds first global push to talk service as well Iridiums standard global voice calling, SMS and SOS. When using PTT, the handheld device gives your team access to unparalleled situation awareness and control features, Iridium Extreme Push to Talk (PTT) Handset features Automatic registration Over the air talkgroup