| 摘要 |
944,161. Automatic phase control systems. RANK-BUSH MUBPHY Ltd. April 11, 1960 [April 9, 1959], No. 11977/59. Heading H3A. An oscillator is synchronised by sync pulses applied to open a diode gate circuit and sample the instantaneous (positive or negative) value of a balanced sawtooth wave derived from the oscillator, the integrated output of the gate circuit phase locking the oscillator so that the sync pulses and midpoint of the long flank of the sawtooth waves coincide. Further, the gate circuit has resistive or time constant means 40 connected across its diagonal, or in one or both of the sync inputs to the gate circuit to limit, during out of synchronism, the change in voltage across output capacitor 26 occurring at sawtooth flyback instants so that instead of the output across capacitor 26 being a sawtooth balanced about zero voltage with sharp flyback, the output flyback is partially suppressed and a .D.C. component arises of polaity indicating the relative sense of the frequency slip (difference frequency) between the sawtooth and sync inputs and speedily restoring frequency equality. The charge limiting resistors may be replaced by constant current devices, e.g. pentode valves, or non-linear resistors. The system may be applied to synchronizing television receiver scanning. |
