Articles about push to talk

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AT&T Launches iPhone Push-To-Talk Service
Facebook Adds Voice Messages to Messenger App; VoIP Calls Being Tested In Canada
AT&T launches enhanced push-to-talk services, hopes to attract Sprint customers over
Sprint shows off Motorola Admiral on video
Motorola Admiral caught on camera
Motorola Titanium arriving on Sprint
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Verizon Push-To-Talk application for BlackBerry smartphones