The Mobile Dialer, which is pre-mapped to a Softswitch, then can be used for making VoIP calls directly from Mobile handset.
Softswitch | softswitch |
In both cases, a SIP-compatible softphone, PBX, or softswitch is configured to place certain (or all) outbound calls through the SIP provider; likewise, the switch or softphone is configured to register with the SIP provider to be notified when a new inbound phone call is available to answer.
Other companies like Symbol Technologies, SocketIP, and Digium have implemented this protocol in VoIP Terminals (phones), Media Gateway Controllers, and Softswitches.