PTT-PoC (How to make VOIP group calling over cellular phone?):
What is push to talk or PTT or PTT-PoC?
According to Wiki, PTT-PoC = Push to Talk over Cellular is a service option which is available for the cellular phone network that allows the customers to make their cell phone to be used as a two way walkie-talkie,
The Push to Talk connection connects almost instantly. The good thing of a PTT-PoC is that it establishes a group connection i.e. any single person can reach an active talk group with only a single press of a button, and that, the user no longer required to dial many calls to talk to a group, so it makes a sense to use PTT while reaching a big group for a voice call, or for voice instant messaging,
Push-to-talk cellular call is termed as half-duplex communication as in this one person calls > the other(s) receives,
And to note that a cell phone call is termed as a full-duplex, i.e. the both of the parties on a call can hear each other at the same real time, and as a PTT is half-duplex, so it simply means that the call or the communication will go only single direction at any single moment of time, so it resembles like a walkie-talkie calling, its become useful when you need to collect some info / have to broadcast an emergency to your group of employees to mobilize them etc. etc.
The advantage of PTT-POC is that it permits group calling by pressing a single button, so one person can make a voice call to whole of the group by pressing only a single PTT button, some PTT networks uses VOIP technology to stream voice over data networks like via a 3G cellular network and this all works digitally,
Though PTT feature is in-built in many cell phones but the PTT-PoC service (Push to Talk over Cellular) depends on the carriers or your Telco!
Free PTT-VOIP (half duplex) Calling with Palringo:
Palringo is FREE PTT provider and supports it on the move, Palringo is for IM, chat, share photos and also send voice messages to all your buddies at a press of a single button, no matter which IM service they use, just press: ‘Push to Talk’ key and you are ready to send the instant voice message, Palringo works in whole of this world and works with number of mobile handsets and OS like: Android, Apple iPhone and , iPod Touch, Blackberry, Java, Symbian and S60, Windows Mobile and many more,
Palringo also holds good for Wi-Fi enabled PDAs / phones, it also works on the laptops / desktops /PC, the best of the Palringo is that its FREE and its push-to-talk (PTTPoC) allows to make you the instant VoIP voice call to your pals just like any walkie-talkie (half duplex) or just like any Nextel phone (Sprint Nextel Corporation).
Read Palringo Blog
Now Push To Talk (PTT-PoC) is available for All Verizon's BlackBerrys:
Verrizon PTTPoC FAQ
PTT and AT&T:
Ventrilo Push to Talk (PTT): VOIP Group Conference Digital Call
Ventrilo is a popular voice communication VOIP software : this software provides for a free real-time voice chat etc for the group communications, Ventrilo supports surround sound and is available for Windows, Mac, Linux OS / platforms. Using Ventrilo PTT hot key you are allowed to make a group conference digital calling,
Ventrilo PTT on YouTube:
Learn Ventrilo's Push-to-Talk Fix for Windows 7 and Windows Vista
Another PTT player is HipVoice which also provides PTT on rugged devices, blackberry, windows mobiles, any cellular or WIFI networks, anywhere in the world (five days trial is free):