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.
NeuVoice is a service provided by NeuWorld Communications, inc. NeuWorld is headquartered in Tampa, FL, however NeuWorld maintains locations in Dallas, Cleveland (Akron) OH and Southern CA (Long Beach area).