| 摘要 |
<p>1,004,673. Automatic frequency and phase control systems. PHILIPS ELECTRICAL INDUSTRIES Ltd. March 9, 1962 [March 13, 1961], No. 9185/62. Heading H3A. A symmetrical transistor 4 acts as a phase detector between incoming sync, pulses 14 and a television receiver line flyback pulses 9, differentiated by capacitor 11 to produce a sawtooth reference wave 16, and producing across an output capacitor 15 an A.F.C. control voltage stabilizing the line oscillator 2. Further, the capacitor 15 is arranged to maintain the extreme, i.e. maximum positive or negative instantaneous values of the sawtooth 16 at instants when the sync. pulses 14 do not coincide in time with the flyback pulses 9 or sawtooth 16, so that this instantaneous A.F.C. voltage, indicating the sense of the frequency error, increases the system pull-in or catching range during conditions of substantial frequency error of the oscillator 2. To this end the transistor 4 is arranged only to receive sync. pulses 14 rendering it conductive when the pulses 14 and flyback pulses 26 (coincident with flyback pulses 9 but opposite in polarity) are coincident in timing on a coincidence detecting transistor 20. The latter is normally conductive to by-pass to earth the pulses 26 but is rendered non-conductive during the pulses 14 so that corresponding width negative pulses (samples of pulses 26) are only during coincidence of pulses 14, 26 passed to phase detector transistor 4.</p> |
