A distributed switching network (switch) routes audio and control signals throughout the switch from various audio sources to one or more audio destinations. Audio sources such as mobile/portable radio units (via RF repeater transmitters), dispatch consoles, and landline telephone subscribers (via the...http://www.google.com.tw/patents/US5365590?utm_source=gb-gplus-share專利 US5365590 - System for providing access to digitally encoded communications in a distributed switching network
