Abstract: In a selectively called radio receiver operable in a battery saving method in which frame synchronism is established after establishment of bit synchronism and in which a bit rate detection signal is produced by detecting a bit rate of an arriving radio signal to establish the frame synchronism before lapse of a frame synchronism establishing interval after establishment of the bit synchronism or restoration of bit synchronism subjected to a failure, repeated production of the bit rate detection signal at a regular interval is monitored by determining for the regular interval a unit time interval shorter than a frame period of the radio signal. Preferably, the unit time interval is equal to a four-codeword length of codewords, such as the frame period, when sixteen is the number of codewords in a typical frame.

Abstract: In a power monitor circuit, AC power-line voltage is converted by a DC power supply to a regulated DC voltage. The DC power supply shuts down itself in the event of a failure therein. The output of DC supply rises from zero to a specified value in slow response to power-on state and drops to zero in slow response to a significant drop in the AC voltage. A rectifier-filter converts the AC voltage to a nonregulated DC voltage. The output of the rectifier-filter rises in quick response to the power-on state and drops in quick response to the significant AC voltage drop. If the output of DC power supply drops below a specified theshold due to AC power-line failure or due to its own failure, a DC low-voltage signal is generated. If the output of rectifier-filter rises above a specified low level a first AC transitory signal is generated and if it drops below a specified high level a second AC transitory signal is generated.