Abstract: A tire (12) used includes a steel belt in its outer circumferential portion. A magnetic sensor (14) including a pair of magnetic detection elements (18A, 18B), which are arranged so that their magnetic detection directions become parallel to each other or series each other, is set in the vicinity of a rear tire (12) in a trunk room of a vehicle (10). Changes in magnetic field upon revolution of the tire (12) are differentially detected by the magnetic detection elements (18A, 18B), and the revolution of the tire (12) is detected on the basis of the differentially detected output waveform. Among a plurality of peaks present in the differentially detected output waveform, a peak, the potential difference from the immediately preceding peak of which is equal to or larger than a predetermined threshold value, is detected as an effective peak, which is effective for tire revolution detection, and the revolution speed of the tire is calculated by detecting the number of effective peaks.

Abstract: A tire (12) used includes a steel belt in its outer circumferential portion. A magnetic sensor (14) including a pair of magnetic detection elements (18A, 18B), which are arranged so that their magnetic detection directions become parallel to each other or series each other, is set in the vicinity of a rear tire (12) in a trunk room of a vehicle (10). Changes in magnetic field upon revolution of the tire (12) are differentially detected by the magnetic detection elements (18A, 18B), and the revolution of the tire (12) is detected on the basis of the differentially detected output waveform. Among a plurality of peaks present in the differentially detected output waveform, a peak, the potential difference from the immediately preceding peak of which is equal to or larger than a predetermined threshold value, is detected as an effective peak, which is effective for tire revolution detection, and the revolution speed of the tire is calculated by detecting the number of effective peaks.

Abstract: An information reproducing system, such as an audio tape player, for automotive use, whereby errors which would otherwise occur when the engine is started are inhibited. The information reproducing system of the invention includes a voltage detector circuit for detecting the voltage of the automobile's battery, an operating unit for operating the recording medium in response to the supply of power from the battery so as to reproduce information stored on the recording medium, and a control unit for controlling the operating unit. In this system, the application of an operation command input to the control unit is inhibited when the voltage detector circuit detects a drop in the voltage of the battery at the time the engine is started. In addition, the inhibition of the operation command input is cancelled when the restoration of the voltage of the battery is detected.