GB881793A - Arrangement for synchronizing pulse generators - Google Patents

Abstract

881,793. Automatic phase control systems. FERNSEH G.m.b.H. Sept. 7, 1959 [Sept. 6, 1958], No. 30443/59. Class 40(5). A pulse train Vf frequency obtained by frequency division from a master oscillator 10 is phase locked with synchronising pulses V<SP>1</SP> by applying both to a bi-stable trigger circuit 3 whose output cyclically varies the frequency division ratio between two integral values, a desired and an undesired ratio, until phase synchronism is reached, the duration of the undesired division ratio progressively decreasing and being proportional to the difference in time between corresponding edges of the two pulse trains. To this end are 18 of the quinary dividers 18-21 may have its division ratio increased to 6 by bi-stable circuit 3 with D.C. output voltage alternated between two valves by the pulses V, V<SP>1</SP>, respectively, the pulse train V causing a drop in collector operating potential of one of the transistors of a transistor multivibrator 18 to which pulses from oscillator 10 are applied so that relaxation delay in one unstable condition is increased and the division factor increased to a higher integral value. Alternatively the division factors of all four dividers 18-21 may be progressively altered. The pulses V, V<SP>1</SP> may be television vertical synchronizing pulses, and the oscillator 10 may be synchronized with incoming horizontal pulses H by applying output pulses A through a binary divider 11, to a sawtooth generator 12 whose output is phase compared with H at 13 to derive a control voltage R locking and stabilizing it, local horizontal synchronizing pulses H being derived from divider 11. V, V<SP>1</SP> are therefore finally synchronized to within half a line of output H.