Abstract: A compression and expansion system comprises a control circuit including a variable impedance element, whose impedance is varied in accordance with a control signal applied thereto. The system has a frequency-response characteristic which varies in accordance with variation of the impedance of the variable impedance element. A control signal is formed in accordance with the level of an input signal and is applied to the variable impedance element of the control circuit thereby to vary the impedance thereof. A switching means forms passing paths in a manner such that, at the time of compressing, the input signal is supplied by way of the control circuit to a negative feedback amplifier. At the time of expanding, the input signal is supplied to the negative feedback amplifier, and, at the same time, the output of the negative feedback amplifier is fed back by way of the control circuit to the input of said negative feedback amplifier.

Abstract: A record disc recording system comprises a circuit for producing a signal which is substantially 2V.sup.2 . a, where; V is the relative velocity between a cutter head and a disc, and a is a specific coefficient, which varies in accordance with the traversing of the cutter head over the disc. A circuit produces a distortion signal {f'(t)}.sup.2 /{2V.sup.2. a - f"(t)} (wherein .vertline.2V.sup.2. a.vertline.>.vertline. f"(t).vertline.) responsive to an original signal f(t) and to the signal 2V.sup.2. a. Another circuit produces a recording signal g(t) with distortion (where g(t) = f(t) + {f'(t)}.sup.2 /2 {2V.sup.2. a - f"(t)}) responsive to the original signal f(t) and to the distortion signal {f'(t)}.sup.2 /{2V.sup.2. a - f"(t)}. A cutter head records the signal g(t) on a record disc.