JPS5512563A - Automatic tracking unit for magnetic recording and reproducing unit - Google Patents

Abstract

PURPOSE:To achieve the reproduction with the best condition at all times, by changing the relative phase of the capstan motor and keeping the reproduced output level around the maximum point always, through the comparison of the reproduced output level of the video signal at present sampling and that immediately before it. CONSTITUTION:The reproduced signal from the rotary head 10 is amplified, detected and A/D-converted and recorded in the memory 14 in the period of the clock generator 17. The comparator 15 compares the content of the memory 14 with the content of the memory 16 sampled immediately before, and if the signal level is increased than that at the period before, level 1 is stored in the memory 24 and if decreased, level 0 is stored. The memory 25 stores the control signal to the updown counter 18 at the period before at 1, 0 level. The coincidence logic circuit 26 counts up the counter 18 further when the memory 24 is at 1 and the memory 25 is also at 1, it counts down when the memory 25 is at 0, and operates the counter 18 in opposite direction as the period before when the memory 24 decreases the reproduced signal level, to drive the capstan servo circuit 20.