GB911409A - Improvements in or relating to pulse generating circuit arrangements - Google Patents

Abstract

911,409. Valve pulse generating and gating circuits. PHILIPS ELECTRICAL INDUSTRIES Ltd. May 5, 1959 [May 8, 1958], No. 15369/59. Class 40 (6). [Also in Group XXXVI] A self-oscillating pulse generator is controlled by input pulses of a much lower frequency supplied through two separate channels, the first channel inhibiting the pulse generator during each input pulse, the second channel discharging a relaxation capacitor in the pulse generator during each pulse so that the pulse generator is ready to start at the end of each input pulse. Fig. 5 shows a circuit for providing the trains of pulses Z from the line and frame synchronizing pulses l, b<SP>11</SP>. Frame synchronizing pulses b<SP>11</SP> are fed to the monostable multivibrator 12, 13, of which valve 12 is normally cut off but is rendered conductive by each positive pulse b<SP>11</SP>, maintaining valve 13 cut off for a time T1 1 depending on the time constant of components 16, 17. The end of period T1 is accurately determined by the appropriate line pulse l. The output pulses b<SP>1</SP>1 drive valve 2 into conduction, cutting off the blocking oscillator 1, the relaxation period of which is determined by capacitor 8 and resistor 9. Pulses b<SP>1</SP>1 also discharge capacitor 8 via a rectifier 5 thus ensuring that valve 1 is able to start generating the train of pulses Z immediately each pulse b<SP>1</SP>1 is finished. Small amplitude line pulses I are fed via capacitor 11 to synchronize the start of each pulse Z with the start of a line. The repetition frequency is stabilized by the catching diode 6 and is adjusted by variation of resistor 9. Pulses are derived from the pulses Z by means of a monostable circuit comprising valves 14, 15. The blocking oscillator 1 may be replaced by a free-running multivibrator.