Patent ID: 6865215

Claim:
A digital data communication overlay system that is overlaid on a predefined frequency band of an existing analog data communication system, the digital data communication overlay system comprising: a first digital data communication unit and a second digital data communication unit; wherein the first and second digital data communication units each have an antenna and are configured to transmit and receive spread spectrum digital data communication signals between each other over a spread spectrum digital data communication channel in which the spread spectrum digital data communication signals are spread over the predefined frequency spectrum using a frequency hopping spread spectrum (FHSS) code including a plurality of hop frequency bands and wherein each of the first and second digital data communication units independently sequentially monitor the digital data communication channel at a selected hop frequency band of the plurality of hop frequency bands to detect AM communication signals received at its antenna immediately prior to transmitting from its antenna in the selected hop frequency band, and the first digital data communication unit is configured to suppress transmission of the spread spectrum digital data communication signals in hop frequency bands in which the first digital data communication unit detects the AM communication signals from the existing analog data communication system.