| 摘要 |
<p>PURPOSE:To perform sure tracking at the reproduction by AGC-processing the video reproduction signal of the horizontal synchronizing signal portion by rotary magnetic heads thereby controlling the voltages to be applied to the piezoelectric elements which vibrate the heads. CONSTITUTION:The heads 9, 10 which are rotated at specified frequencies by phase servo controlling are vibrated by the sine wave signals of specified frequencies applied to piezoelectric elements 7, 8. The envelope of the reproduction signals by these heads 9, 10 is applied to a detector 27 and AGC circuit 29, and is subjected to AGC control by a current variable element 94 such as FET, etc. at the response frequency of 1Hz of the circuit 29, whereby it is made to the d.c. voltage of less noise components corresponding to either of the tracks of the heads 9, 10 having been removed of low frequency amplitude variations. This voltage is passed through a horizontal synchronizing signal separator circuit 30, gate signal generating circuit 31, gate circuit 32 whereby it is synchronized with the horizontal synchronizing period, after which it is processed in a clamping circuit etc. to control the applied voltages of the elements7, 8.</p> |
