How ''Push To Talk" system works in the mobile phones?

They work the same way that the nextel wakie talkie feature works. I have that feature from U.S. Cellular, and it works through the internet type connection. As long as you have the internet feature, all you have to do is push a button and talk you someone who has the same type of feature on their phone. there is no number to dial once you have your phone set up. But this doesn't work for all phones. As far as distance limitations, it shouldn't matter, as long as you are in a coverage area. If there is no signal, then it won't work.