GB959778A - Circuit arrangements for the production of a train of advance pulses - Google Patents

Abstract

959,778. Automatic phase control systems. FERNSEH G.m.b.H. Aug. 25, 1960 [Aug. 25, 1959], No. 29353/60. Heading H3A. [Also in Division G3] Pulses B are produced with leading edges in advance of those of reference pulses A by a predetermined time automatically rendered constant. Negative-going reference pulses A of repetition period T switch over a multivibrator 1, 2 and reduce the grid potential C of valve 2 by a fixed amount, but capacitor 5 then charges through resistor 8 from a fixed potential P until after a constant time (T-t) valve 2 again conducts and after a further time t is cut-off again by the leading edge of the next pulse A. An advance negative going pulse B (advanced in time by its own duration t) is therefore generated at the anode circuit of valve 2 or a parallel coupled valve 10. If the recurrence period T of A varies the output pulses B of valve 10 will tend to vary in duration t (T-t being constant) but since the voltage at integrating point P is fed back to C to vary the instant of re-conduction of valve 10 the duration (advance time) t is made constant. In Fig. 4 positive-going pulses D charge negatively, through a valve 23, and capacitor 24 and rectifier 25, a timing capacitor 4 which discharges through resistor 7 from point P until valve 10 is again conductive whereupon leading edges of negative output pulses B<SP>1</SP> are generated and terminated after a further time t by the next following pulse D. Pulses B<SP>1</SP> are therefore generated of duration and advance timing t, and this duration t is maintained constant by feedback from P to the grid of valve 10, and by the voltage at P, through valve 31, varying the anode voltage of valve 23 and hence the charge and voltage applied to capacitor 4 at each pulse D. In a modification, with valve 31 omitted, advance pulses B<SP>1</SP> with steep leading-edges are produced by applying the anode voltage of valve 10, through a phasereversing valve and forwardly conductive rectifier diode, to the grid of valve 10 as positive feedback. The advanced pulses of constant duration may be used as television receiver blanking pulses during the flyback intervals.