Dictionary:Ac-bias recording

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A system in which a modulating message biases a constant-amplitude carrier. See Figure M-16. Used in magnetic tape recording to avoid hysteresis distortion.

FIG. M-16. Modulation types. (a) The message directly. (b) Amplitude modulation (AM); the amplitude of the carrier wave varies as the message. The amplitude of the carrier and its mirror image is the signal. (c) AC-bias modulation; the bias varies as the message. (d) Frequency modulation (FM); the frequency of the carrier wave varies. (e) Pulse-width modulation (PWM); the width of pulses varies. (f) Pulse-spacing modulation; the timing of pulses varies. See also Figure D-23.