| 摘要 |
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.
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