AF recording system for magnetic tape - has amplifier and reference signal generator and uses polarisation current which is varied dynamically for optimum value

摘要

During recording of audio frequencies onto magnetic tape a polarisation current is also recorded. This current is varied dynamically to be close to optimum value for information being recorded. In an audio frequency recording system the signal is amplified and passes through fixed high pass filter and adjustable filter. Amplifier reduces noise level and signal is further amplified for rectification. This signal is smoothed and fed back to control filter frequency range. The smoothed signal is also passed to threshold circuit to provide control signal for generating polarisation signal which is recorded with compressed audio signal from summer amplifier.