A soft switch 134 providing wireless PBX voice services to a local area network (WLAN) is used to extend PBX functionality to the cellular domain. A dual mode remote unit is capable of receiving signals both in the cellular system as well as the WLAN. The cellular system is comprised of a data-bearing...http://www.google.com.tw/patents/US20060025141?utm_source=gb-gplus-share專利 US20060025141 - Extension of a local area phone system to a wide area network with handoff features
