Abstract: An on-site selective call receiver interacts with a wide area selective call system to increase the probability of timely message reception by a selective call receiver capable of operating in either the wide area or the on-site selective call system. A frequency shifting signal is transmitted from the wide area system in response to addition of the selective call receiver to the on-site registry or automatic detection of entry of the selective call receiver into the on-site selective call system coverage area. The selective call receiver shifts to the wide area frequency in response to detecting that the receiver is out of range of the on-site system signal or in response to a signal transmitted by the on-site system in response to deletion of the receiver from the on-site registry or detection of the exit of the receiver from the on-site coverage area. The on-site system increases message throughput by interleaving data messages with voice messages.

Abstract: A battery charging device wherein the charging current level is controllable by a thermal circuit responsive to battery temperature also includes a circuit responsive to battery voltage and a timing circuit. The timing circuit is activated when a battery is inserted into the device for charging and immediately times a very brief interval. If the battery voltage exceeds a predetermined level during the timed interval, the charging current level is reduced as by the thermal circuit. The circuit protects both cold and charged batteries from damage due to overcharging.