Ultrasonic generator for audio tape recorder read-write heads - provides erase current from LC circuit of which inductance comprises winding for erase head

摘要

The tape recorder has at least one read/write head which receives an hf polarisation or pre-magnetisation current during recording, and an erase head which receives hf erase current under the same conditions. The currents are produced by at least one oscillator comprising an LC resonant circuit whose inductance comprises the coil of the erase head. The oscillator consists of two complementary push-pull transistors connected together via two resistors at their emitters, to the supply poles at their collectors, and to two divided voltages along a three-resistor voltage divider at their bases. The junction between the emitter resistors is connected to the LC resonant circuit. The voltage divider is coupled via two capacitors to the LC circuit.