Abstract: A battery voltage detection system, suitable for a photographic device, having a battery power source. The battery voltage detection system includes a circuit to generate varying periodic signals, such as PWM control signals, and a battery voltage detection device to measure the battery voltage a plurality of times within a predetermined time period and to detect the battery voltage based on the plural battery voltage measurements. The battery voltage detection device performs the plural measurements of the battery voltage during the generation of the varying periodic signals. The plural measurements are combined by taking an average value or a root mean square value of the battery measurements to determined the battery voltage. The battery voltage detected by the battery voltage detection device is then compared with a predetermined standard value to determined the state of the battery.

Abstract: In an optical or magneto-optical recording and/or reproducing apparatus, an apparatus for locating a pre-designated one of a large number of tracks on the recording medium by a light beam at a high speed during signal recording, reproduction or erasure. The light beam irradiated on the recording medium is swept in the direction of traversing the tracks, the reflected light of the light beam from the recording medium is detected by a photodetector, and a predesignated one of the tracks is retrieved on the basis of the results of detection of the reflected light. The sweeping movement of the light beam is controlled by feedback control of the track traverse velocity of the light beam prevailing until the beam gets to the predesignated track.