sync separator

elektor july/august 1985 Many monitors have separate inputs for the line (horizontal) and field synchronization pulses. If your com- puter only provides composite sync pulses, the circuit described here makes it possible to split the com- posite sync signal, CSYNC, into proper line, HS, and field, VS, pulses. It is possible to feed the CSYNC as line sync pulses direct to the monitor, which is the reason that the CSYNC input is connected direct to the HS output terminal. R3 RI R2 CI C2 18,1 27n 5 14 16 6 C l 0 R C 2 0 OAl r!D iCi CSYNC 74LS123z 131 CLR1 CLR2 01 31 111 131 9t 8 0 5 V 15 mA VS HS 01 sync separator To derive the field sync pulses from the composite signal, a dual retrig- gerable monostable type 74LS123 is needed. The first mono period is slightly longer than the distance between two line sync pulses. As the monostable is retriggered by each line sync pulse, it only resets in the absence of a line sync pulse, that is, at the onset of a blanking interval. The period has...