Abstract: A system for monitoring a battery voltage level and A.C. power supply. The A.C. power supply and a backup battery are used to power a voltage regulator which provides a reference voltage to the system. A first comparator circuit senses a drop of the voltage from the monitored battery below a predetermined level and provide a signal in response thereto. A second comparator circuit senses the loss of A.C. power and produces a signal in response thereto. A backup battery provides power to the system in the event of the loss of A.C. power. The signals produced by the comparator circuits activate a timer which in turn activates an alarm to indicate a problem in the system. The timer may be automatically deactivated by a return of the battery voltage level above the predetermined value to prevent false alarms. A second timer is also provided to provide deactivation of the alarm during servicing of the system. The system is designed so that the alarm will be sounded in the event of loss of A.C.