In order to make phone calls via the Internet one’s device has to be compatible with Softphone software. In example in order to call from a PDA using VoIP technology one has to install Softphone software, in order for it to work properly, PDA has to have Softphone compatibility.
Citel Technologies , A Voice over IP Phone company that provides VoIP Business Phone Systems. Its Main products include EXTender, PBXgateway, Upgraded Hardware Products, PBX platforms etc.