When you receive an incoming call to your phone number, your other telephones (cell, home phone, car phone) will ring as well and the first one answered will be connected to the caller. Basically the call will be routed to all phone sets, which you will list in simultaneous ring option.
IXC Softwitch is a high performance scalable Class 4 VoIP Softswitch solution with user friendly GUI web interface, which enables secure large VoIP traffic flow over various IP networks.