SU1688450A1 - Frame sync pulse selector - Google Patents

Abstract

The invention relates to a technique of television and can be used for the selection of frame sync pulses. The purpose of the invention is to improve the accuracy of selection and ensure the stability of the sync pulse. The frame sync selector contains a pulse shaper, multivibrators 2 and 3, element 4, trigger 5 and pulse counter 6 Shaper 1 allocates the leading edge of the horizontal sync pulses, according to which the multivibrator 2 generates a pulse with a duration of more than half the period of the horizontal sync pulse but more equalizing, and multivibrator 3 pulse with a duration shorter than the duration of horizontal sync pulses At the output of counter 6, a signal is generated at the front of which the trigger 5 is set to one and returns to zero at the output of the element And 4 2il

Description

Fig

The invention relates to a television technique and can be used for the selection of frame sync pulses.

The purpose of the invention is improving the accuracy of selection and ensuring the constancy of the duration of the sync pulses.

Fig. 1 shows an electrical block diagram of a frame sync selector, Fig. 2 shows timing diagrams explaining its operation.

The selector sync pulses (Fig 1) contains the driver 1 pulses, the first 2 and second 3 multivibrators, element 4, trigger 5. counter 6 pulses.

The selector staffing clock works as follows.

The sync pulse arrives at the input of the pulse shaper 1, which selects the leading edge of the horizontal sync pulses (SSP) and inverts them (Fig. 2.a). The inverted signal from the output of the imaging unit 1 is fed to the input of the first multivibrator 2 (performed without restarting), as well as to the input of the second multivibrator 3 and to the input of the element 4. The second multivibrator 3 generates pulses of a high logic level with a duration less than the length of the horizontal pulses, but more equalizing (figure 2, b). These pulses from the output of the second multivibrator 3 arrive at the input of element 4, as a result of which a high level impulses appear at the output of element i / i4 at the time of equalizing pulses (fig. 2, c). From the output of element 4, the first equalizing a pulse nocrvn.im ml R the fruit of trigger 5 and translates it into a state of low logic level. Four more equalizing impulses that came after the first one are also identified by the AND 4 element and are fed to the R input of the trigger 5, but they can no longer change its state.

The low logic signal from the output of the trigger 5 is fed to the reset input

counter 6 and enables the account. The input of the first multivibrator 2 is supplied with a signal from the output of the driver 1 pulses. Input pulses generate pulses with a duration of more than half a line, at which equalizing and field pulses are filtered. From the output of the first multivibrator, 2 line pulses with a duration of more than half a line are fed to the counting input of counter 6, triggered by a level difference. Thus, the counter 6. starting from the formation of the leading edge of the field sync pulse, is counting the lower case

sync pulses. At the time of the arrival of the next horizontal sync pulse, determined by the necessary division factor at the output of counter 6, a signal is generated that arrives at the input of trigger 5 and

translating him to a high logic level

The high logic level signal from the output of trigger 5 goes to the R input of counter 6, zeroes it and disables counting before the arrival

Claims (1)

of the next field pulse This ensures the constancy of the duration of the framing sync pulse. Claim Invention Personnel Clock Selector, containing a serially connected pulse shaper and a first multivibrator, the element I and a trigger characterized in that, in order to increase the accuracy of selection and ensure the durability of the clock pulses, a second multivibrator is introduced, the input of which is connected to the first input of the element And and with the driver of the pulse generator, and the output connected to the second input element And, the output of which is connected to the R input of the trigger, as well as a pulse counter, the information input of which is connected to the output of the first multivibrator, input O is connected to the trigger output, and the output is connected to the S-input of the trigger Lower Pulse Equalizing FIG. 2