Time base correction apparatus

A time base correction apparatus comprising:

• a disc-shaped recording medium having a signal track;
• first drive means for rotatably driving said disc-shaped recording medium;
• transducer means for reproducing signals recorded on said signal track of said recording medium;
• second drive means for moving said transducer means from one scanning position to another relative to said recording medium in a reverse direction of said signal track of said recording medium, responsive to a first control signal applied thereto;
• reference signal generating means for generating a reference signal;
• first control means receiving said reference signal, for controlling said first drive means to rotate said recording medium in phase synchronism with said reference signal;
• synchronizing signal detection means for separating a synchronizing signal from signals reproduced by said transducer means;
• variable phase means receiving said reference signal and a second control signal, said variable phase means including fourth control means producing an output which is controllable in synchronism with said reference signal and which has a phase which varies in accordance with said second control signal;
• phase comparison means for providing an output signal representing a phase difference comparison of a phase of said separated reproduced synchronizing signal with a phase of said output of said variable phase means;
• third control means receiving said output signal of said phase comparison means and applying it to said second drive means through a switching circuit, said output signal being provided to said second drive means through said switching circuit comprising said first control signal;
• an integrator circuit receiving a third control signal, said integrator circuit having a time constant which varies in accordance with said third control signal;
• second control means providing an output signal of said integrator circuit to said variable phase means, said output signal of said integrator circuit comprising said second control signal;
• detecting means receiving said output signal of said phase comparison means and for determining whether said output signal of said phase comparison means is within a predetermined range;
• actuating means for actuating said switching circuit to pass said first control signal responsive to a said output signal from said detecting means indicating that said output signal of said phase comparison means is within said predetermined range;
• and
• circuit means receiving said output signal from said detecting means and applying it to said integrator circuit to control said integrator circuit to have a predetermined small time constant when said output signal of said phase comparison means is not within said predetermined range and a predetermined large time constant when said output signal of said phase comparison means is within said predetermined range.