Abstract: A dither-controlled automatic scan tracking system for television signal playback includes a field-store memory for storing a scan track control signal related to the average amplitude-tune "shape" of the transducer deflection control signal. The memorized scan track signal is added to a wideband scan track feedback signal to produce a composite signal which improves tracking error. Anomalous errors can result from memorizing signals which are systematic but unrelated to transducer or head deflection from the track. The errors are reduced by reversing the dither phase each television field, thereby allowing those signals unrelated to deflection to be identified and cancelled. The dither phase reversal can be switched or a continous phase progression.

Abstract: A dithered automatic scan tracking system for a videotape playback machine includes a bimorph which with its associated load has a mechanical resonance. In special-effects operating modes, the jump or reset signal which drives the bimorph at the end of its scan to position the playback transducer for the next track excites the mechanical resonance, which causes incorrect demodulation of the detected FM envelope and therefore causes generation of an incorrect AST loop error signal until the excited resonance dies away. A gated phase-lock loop is coupled to the bimorph position sensor and produces clock signals for control of the demodulation of the detected FM envelope. The gate decouples the position sensor from the phase-lock loop during recurrent intervals including those intervals during which the mechanical resonance is excited. This allows generation of a correct error signal immediately after the jump and reduces mistracking.

Abstract: A recorded medium moving at some operational velocity is rapidly stepped to advance or retard the position thereof by a preselected time segment relative to a reference clock and the stepping cycle is completed simultaneously with the recorded medium being returned to its operational velocity.

Abstract: A recorded medium is brought to its operational velocity at which a phase lock is simultaneously achieved between a recorded sync signal thereon and an external reference sync signal, during a rapid framing cycle that corresponds in time with the duration taken by the recorded medium to travel through a distance equal to two consecutive spaces between recorded sync signal pulses.

Abstract: A motor speed control circuit features a speed synthesizer for accurate speed control. The synthesizer has a phase-locked loop with a programmable divider for allowing variable speeds.

Abstract: A color framing circuit is usable for both PAL & NTSC video signals. To do this, it detects the direction of zero crossings of the color burst with respect to the preceding horizontal sync pulse for at least two consecutive lines.