Push-to-talk communication has been around since two-way radio came into use more than 70 years ago. Now, AT&T is putting a new spin on the sub-second communication feature with an enhanced push-to-talk service that can instantly reach up to 250 people simultaneously. It uses Internet Protocol as the conduit instead of radio frequencies.

Steve Colkitt, IT director at CourierNet, which beta-tested the service, compares it to Motorola's pioneering iDEN (integrated digital enhanced network) service, which combined two-way radio capabilities with other features, such as pagers and fax/modem. "It's damn near iDEN quality, which no one's been able to duplicate," he says.

The service is a downloadable application that can be installed and run on AT&T phones, which include a ruggedized waterproof model.

ENR reviewed AT&T's new application on Android devices. It works by helping the user create batches of contacts from a phone's contacts. When the user selects a batch, or group, to send messages, a large green button appears on screen. As long as the button is held in, the caller can speak, and his or her voice will be audible almost instantly on the phones of the contacts who are running the application. All members in a batch can be reached simultaneously.

An on-screen phone symbol conveys the user status of the contacts. If a contact is available, the phone appears green; if the app is turned off, the phone is red; and if the device is off or the app force-closed, the symbol is gray. If the phone is green, the contact will be interrupted immediately by the caller's voice. In ENR's test, calls traveled to servers in Houston and back to New York City instantly.

The AT&T release comes ahead of a Federal Communications Commission mandate that all VHF and UHF services operating on the 25-kHz bandwidth, on which existing push-to-talk service is lodged, must be converted to 12.5-kHz or less by January 2013, so more channels can coexist in the same band. AT&T's app, which will launch later this year, could serve as a replacement as the new rule phases out older services.