Abstract: A magnetic field generating member is attached to a rotable object the angle of which is to be detected. The apparatus includes first and second magnetic sensors located in the magnetic field generated by the magnetic field generating member, first and second detectors for generating first and second sine wave singles responsive to outputs of the first and second magnetic sensors, first and second limiters for limiting the first and second sine wave signals; and, a synthesizing circuit for synthesizing outputs of the first and second limiter to thereby obtain a synthesized output.

Abstract: A displacement measuring apparatus including a variable inductance coil formed of a pair of coils, on a core of predetermined length made of a material having high magnetic permeability. The pair of coils are disposed on a core adjacent to each other in their axial directions and are covered by a metal sleeve of substantially the same length of one of the coils. A detecting circuit is provided including a high frequency oscillator and a rectifier and is connected to the variable inductance coil, wherein when the metal sleeve is slidably moved, the detecting circuit generates a direct current voltage in correspondence with the displacement of the metal sleeve.

Abstract: A magnetic detector for detecting the magnetic field of a magnetic field generating substance including an even number of saturable coils aligned in a straight line with the distance between adjacent ones larger than the width of the magnetic field generating substance. The saturable coils are separated into at least two pairs, and a high frequency oscillator is provided to supply a high frequency voltage through a resistor circuit to each pair of the saturable coils. A rectifying voltages circuit is arranged across the resistors in a differential manner as an output. When the magnetic field generating substance is displaced over an interval wider than the width thereof relative to the saturable coils, the magnetic detector generates a linear output voltage.

Abstract: A verifying device for a key card on which a magnetic signal is recorded is formed of a set card on which a predetermined reference magnetic signal is recorded, a magnetic sensor consisting of a saturable core and a winding wound thereon, an oscillator for supplying a voltage to said winding, a switching element connected to the winding, a power source connected between both ends of the switching element, and an output terminal led out from one of both ends of said switching element.

Abstract: A system for recording and reproducing both still pictures and sounds related to such pictures employs a magnetic tape having index signals at intervals therealong to identify respective portions of the tape which is moved in a predetermined path to bring a selected tape portion to a recording and reproducing station at which video signal and audio signal magnetic heads are moved at relatively high and low speeds, respectively, across the path, preferably obliquely thereto, for scanning respective stripe-like areas on selected tape portion, and the heads are operated during the movement thereof to selectively record and reproduce video and audio signals in the respective stripe-like areas being scanned thereby.