Abstract: A communications system for use by workers in a confined hazardous working location includes a transmitter that is carried by the worker in the hazardous area. The transmitter is capable of sending either an alarm signal or a check-in signal to a centrally located monitoring and control station. The monitoring and control station includes a receiver for receiving the signal from the transmitter and further includes an alarm that is activated upon receipt of an alarm signal from the transmitter. The receiving unit further includes a timer that automatically activates an alarm signal upon the expiration of a predetermined amount of time. The timer in the receiver is initialized by receipt of a check-in signal from the transmitter. The transmitter includes a warning subsystem that alerts the worker of the impending expiration of time on the receiver timer to permit the worker to check in and reinitialize the receiver timer, thereby eliminating false alarms.