Tape recorder sound head demagnetiser - has electromagnet with gap yoke and exciter circuit feeding AC decreasing amplitude

摘要

The central part (2) of the magnet yoke (1) of the demagnetiser is made higher on both sides of the gap (3) than a standard magnetic tape is wide. The yoke areas (8) adjoining it towards the outside are less high than the tape is wide. The exciter circuit consists of an electronic switch (4) and a d.c. voltage transformer (3) supplied by a battery (1). It also contains a change capacitor (2) and an oscillator (5) supplied with power from it and connected to the electromagnet. When a predetermined charging state is obtained in the capacitor the latter is disconnected from the transformer and connected to the oscillator.