Determining transmit time of a received signal in a simulcast multi-site communication system begins when a communication unit transmits a message to one or more network receivers. Each receiver transports the received signal with a time stamp to each transceiver in the network via a digital communication...http://www.google.de/patents/US5455965?utm_source=gb-gplus-sharePatent US5455965 - Method for determining and utilizing simulcast transmit times
