The design requirements of a pick-up and arm suitable for use in quality control of records are presented. It is shown that for accurate tracing of records the dynamic mass of the cantilever must be 1 milligramme or less, and the compliance must not be less than 4 x 10/-6 cm/dyne. Damping of the arm is necessary if the pick-up is to remain in contact with the groove walls under adverse conditions. Performance of the pick-up includes a wide frequency response, good channel separation and ability to reproduce faithfully the recorded waveform. Wear of both stylus and record is considerably reduced due to the small dynamic mass of th'cantilever and by complete control of unwanted resonances.
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