Abstract: A method and system of radio data communications especially useful in communicating over a special communications channel between a base station or cell site of a cellular telephone system and one of many user stations. Each user station communicates an alarm condition which may be either a burglar type alarm or an environmental alarm to the base station by responding on a compelled basis to a status request from the user station. The responses to such request are prevented from overlapping by fixed and unique time delays for each user station. This status response requires substantially a single bit width of data. If no response is received, this is also sensed. Secondly, a different category of request acquires from each selected user station several bits of data constituting an informational message, the request being sent to each user station in a cell in sequence, along with the particular unique time delay for each user station.

Abstract: An improved AMPS cellular system where non-interfering digital communication channels are added to the existing analog or digital voice communications channels in the system by utilizing frequency space between channels made possible by the AMPS co-channel and adjacent channel frequency coordination procedures. Interference is prevented by reduction of power, selection of frequencies, proper modulation and demodulation techniques, and unique allocation to the channels in frequency and location. The system is also applicable in general to the insertion of narrow frequency bandwidth channels in any existing communications system using co-channel and adjacent channel frequency allocation strategies.