US Patent 7512406 Personnel tracking system

The system for tracking and communicating with individuals as they move through a complex structure involves wireless communication over a first channel, called herein a front channel, between transceivers carried by the individuals being tracked and repeaters. This provides distance information signals between repeaters and transceivers within range of each other. In a second or back channel, this distance information is transmitted between repeaters until it reaches a command station. At the command station, the distance information is employed to calculate the real-time position of the individual carrying each transceiver and to plot that position on a map for display at the command station. A similar front channel and back channel approach is used to provide audio information from mobile voice communication devices carried by the individuals being tracked. Audio repeaters on a front channel communicate with these voice communication devices and on a back channel send the audio information through various audio repeaters to the other voice communication devices in the system.