Abstract: A personal alarm system includes a monitoring base station and one or more remote sensing units in two-way radio communication. An electronic handshake between the base station and each remote unit is used to assure system reliability. The remote units transmit at selectable power levels. In the absence of an emergency, a remote unit transmits at a power-conserving low power level. Received field strength is measured to determine whether a remote unit has moved beyond a predetermined distance from the base station. If the distance is exceeded, the remote unit transmits at a higher power level. The remote unit includes sensors for common hazards including water emersion, smoke, excessive heat, excessive carbon monoxide concentration, and electrical shock. The base station periodically polls the remote units and displays the status of the environmental sensors. The system is useful in child monitoring, for use with invalids, and with employees involved in activities which expose them to environmental risk.

Abstract: A self-locating remote monitoring system (750) includes a supervising base station (754) and one or more remote monitoring units (752). A remote unit (752) includes a navigational receiver (756) operating with an existing navigational system for providing a remote unit location (759) and includes a transmitter (758) for communicating the location (759) to the base station (754) for display (772). The remote unit (752) includes one or more physiological/environmental sensors (760) for monitoring at the remote location. In a specific embodiment a change in sensor status (761) results in the status and the location being transmitted to the base station (754). The base station (754) includes alarms (776) and displays (772) responsive to the change in status. One embodiment defines a man-over-board system (300) which combines water immersion (308) and distance (334) from the base station (318) to trigger an alarm (332) and begin location tracking (324).