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PTT
It is a two way talking service, more or less like a walkie talkie. In this communication will be possible at one direction at a time. The speaker has to press the PTT button through out his speech. He can release the button only when he has finished what he had planned to convey. The other person at the other end will has to follow the same method. Most PTT services allow group calling, in which one person will be talking to a group of people.
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