Cingular announced that it has added push-to-talk service to its cellular offering. The carrier said its P2T coverage area is the largest in the U.S. The service lets users know when other P2T subscribers are available and lets users create pre-determined talk group or create them on an impromptu basis. It also converts P2T talk calls to cellular calls; the function works on calls of up to 20 participants, effectively creating mobile conference calls, Cingular said. Two P2T handsets initially will be available: the Samsung d357 and the LG F7200.