Abstract: The gain of an envelope detector circuit for detecting the envelope of a signal read from a magnetic head is capable of being changed over between two, namely high and low, stages. The gain of the envelope detector circuit is raised when track search processing is performed. When peak position detection processing is executed for detecting the peak position of the envelope of a recorded signal with regard to a designated track, first the gain of the envelope detector circuit is raised. The gain is lowered when the envelope saturates. This makes it comparatively easy to perform envelope detection, shortens the time required and makes it possible to use even a relatively low-precision A/D converter in the envelope detector circuit.

Abstract: An apparatus for use with a compact disc for writing and reproducing data into an arbitrary sector or rewriting data of an arbitrary sector by allowing the selection of an interleave process similar to that in a music type compact disc or an interleave process of a length corresponding to one recording unit (sector) to thereby make possible sector-completion type encoding and decoding.

Abstract: A differential amplifier (15, 16) which drives a recording head and is located on the headwheel which carries the recording head is equipped with automatic switchover provided by a transistor (18) in series with a resistance and the emitters of the differential amplifier. In the absence of signals in the rotor of the rotary transformer which supplies signals to be amplified for recording, this differential amplifier has substantially no idling current, but in response to the presence of a signal in the rotor, a switchover signal is provided making the transistor (18) in the emitter circuit of the differential amplifier conductive and putting the differential amplifier into class A operation. As a result, digital video signals can be recorded at a high data rate without distortion, whereas unintended erasure of the magnetic tape by direct current components in the winding of the recording head is prevented.

Abstract: An improved detection device for detecting whether a tape is a normal tape or a chrome or metallic tape and for detecting whether the recording head is at an eject position, a stop position or a recording/reproducing position. The device includes an operating piece movable in accordance with the movement of the recording head, a switching piece for turning ON and OFF a switch, the switching piece having a cam surface engageable with the operating piece, a detecting piece having a cam surface engageable with the operating piece and having a detecting portion insertable into a tape characteristic hole formed in a cassette half, and a second switch adapted to be turned ON and OFF in accordance with the movement with the head.