Center City Communications offers IP (Internet Protocol) Phone systems, which uses software for operating the phone system on a server within the office. 

An IP PBX is the best option for businesses that want to own their phone system, but still want some of the mobility features, while also having a fully unified communications system. 

With an IP PBX  businesses can also use this system for conference calling, or use features such as "find me", "follow me", which allows businesses to see people's current availability and location.

The IP PBX system also includes features such as chat, barge or whisper. Businesses should consider this option if most of their workforce is located in office, and have fewer remote workers.