A data communications system is described that covers a geographic area divided into a plurality of non-overlapping zones and includes a general communications controller (GCC), a plurality of channel communications modules (CCM) and associated transmitters and receivers, and a plurality of portable...http://www.google.com.hk/patents/US4550443?utm_source=gb-gplus-share專利 US4550443 - Method and apparatus for dynamically selecting transmitters for communications between a primary station and remote stations of a data communications system
