Patent GB-1188571-A (GB)
Title: Television Vertical Sychronizing Signal Generator
Inventor: NISHIMURA TAKESHI
IPC: H04N5/12
Filed: 1967-07-20
Abstract: 1,188,571. Television. HITACHI SEISAKUSHO K.K., and HITACHI DENSHI K.K. 20 July, 1967 [20 July, 1966], No. 33331/67. Heading H4F. A generator for generating a television vertical synchronizing signal for use in conjunction with a horizontal synchronizing signal to accomplish interlaced scanning comprises an oscillator 1, Fig. 1, which generates rectangular waves of 50% duty factor having a period equal to 2 N (where N is the number of scanning lines per field) times the period H of the horizontal synchronizing signal, Fig. 2a, a differentiating circuit 2, rectifiers 3 and 4 of opposite polarity and a polarity converter 6 which produce pulse trains c and f, Fig. 2, of period 2 NH phase displaced by NH, and a delaying circuit 5 which delays pulse train c by H/2 relative to the phase of pulse train f to produce pulse train d, pulse trains d and f being combined to form the train g which is delayed by H/2 at every other pulse and this output is used to trigger an oscillator 7, whereby a vertical synchronizing signal, Fig. 2h, is produced capable of effecting interlaced scanning. Instead of oscillator 1 comprising an astable multivibrator it may comprise a multivibrator or a blocking oscillator (8, Fig. 3, not shown) oscillating with a period NH, used to trigger a bi-stable circuit (9). The delay means may comprise a monostable circuit (12, Fig. 3, not shown) operated by pulse train c to generate output pulses of width H/2 which pulses are differentiated and rectified to produce pulse train d. To fix the phase relationship between the horizontal and vertical deflections, oscillator (8) of period NH is synchronized by a horizontal deflection frequency oscillator. In a further embodiment, Figs. 7 and 8, output n of oscillator 15 of 50% duty factor oscillating at the horizontal deflection frequency is transformed by differentiating rectifiers 16 and 17 into pulse trains o and p phase displaced by H/2. Pulse train p triggers oscillator 8 oscillating at the vertical deflection frequency to produce output j of period NH. Output j causes a bistable circuit 9 to operate and produce outputs a and k, which upon passing through differentiating rectifiers 10 and 11 cause pulse trains c and f to be produced. A bi-stable circuit 18 is triggered by pulse trains o and c to produce output pulses q of width H/2. Output q is differentiated and rectified 19 to produce pulse train d, which with pulse train f causes a bi-stable circuit 20 to produce outputs r and s. These outputs are differentiated and rectified 21, 22 and combined to produce pulse train g which is delayed by H/2 at every other pulse, and this output is used to operate oscillator 7 to obtain the desired vertical synchronizing signal. Pulse trains d and f may be combined and used to operate bi-stable circuit 20 to obtain pulse train g directly. Oscillator 15 may comprise an oscillator with a frequency twice the horizontal deflection frequency, the output of which triggers a bi-stable circuit, Fig. 9 (not shown), or a horizontal deflection frequency oscillator, the output of which is amplitude limited and amplified, Figs. 10 and 11 (not shown).