Half-duplex communication system for telemetry modems

Data transmission by a half-duplex transceiver over a full-duplex cellular telephone system using the EIA/TIA-553 standard is achieved by monitoring the forward channel to synchronise the transceiver with the forward channel signal, switching to transmit mode to transmit data on the reverse channel, and momentarily switching back to receive mode during the transmission at the projected times of occurrence of significant status bits on the forward channel in order to detect status bits whose timing controls operation of the transceiver.