Disc and videodisc reader head positioning control system

Claim 1

A control system for positioning the reader head of a videodisc reader of the type wherein a picture corresponding to a television frame is recorded on a videodisc track, each recorded television frame including an identifying indication, said control system comprising means for operating said videodisc reader in a picture stop mode, a picture identity detector including a first memory for storing the detected picture identity, means for providing a desired picture identity including a second memory for storing the desired picture identity, control means for causing a relative movement between said reader head and said videodisc, and a control circuit for said control means, said control circuit comprising an up-down counter, means connecting the output of said first memory to a preset input of said up-down counter, a comparator having one input connected to the output of said up-down counter and a second input connected to said second memory, whereby said comparator provides an output signal indicative of the difference between the desired picture identity and the contents of said up-down counter, a logic decision circuit having its input connected to the output of said comparator, said logic circuit including means responsive to the output of said comparator for operating said control means so as to reduce said difference to nil and simultaneously deliver pulses to said up-down counter corresponding to an output of the control means, said logic circuit having an output delivering a signal when its input signal is nil, said output of said logic circuit enabling said means operating said videodisc in said picture stop mode.