| 摘要 |
This servodevice for synchronising the scanning of helical tracks on a magnetic tape with the revolution of the magnetic heads is used in the recording and replaying of television signals. For this purpose, command signals (Pb) with a particular phase relationship with respect to the position of the rotating magnetic heads (H1, H2), either from a pulse transmitter (P) during the recording or from the recorded information during the replaying are used. Reference signals (Pa) and command signals (Pb) are supplied to a flip flop (21) as phase comparator in order to generate by this means an information on the mutual position of the said signals. A signal processing circuit (24, 25) is used for generating selective information (Pf, Pg) on leading or lagging phase angle. The signal from an up/down counter (15) and a variable phase delay circuit (3) is applied to a drive control (4) for the drive (1) of the magnetic heads. This provides simple and inexpensive control for avoiding low-frequency phase errors, namely a DC drift and high-frequency phase errors, namely synchronisation errors. <IMAGE> |
