Disc recording of electro-magnetic signals - disc shaped increased as diameter reduced during recording and reproduction

摘要

One zone of disc carries signals used for obtaining constant speed of recording/reproducing. For this signal a spiral ridge is made during manufacture with a frequency of the signal to correspond to the reproducing frequency (i.e. in television). The other, the magnetic zone has its distance from the ridge predetermined during manufacture of the disc. For production of the matrix for ridge cutting the turning speed of the tool is variable so as to give constant cutting speed, the impulses and frequency being constant over the complete cutting range. Control circuit comprises discriminators and comparators of volts, frequency and phase. Also convertors are provided which, after picking up the signal and comparing it with the reference, adjust the driving motor to give constant pick-up speed. P.V.C. can be used for the "ridge zone" and polyester for the magnetic zone.