On Fri, 13 Mar 1998 19:58:36 +1000 Tony Antoniou writes: >Easiest is to use a National Semiconductor LM1881 Sync Separator which If you have $6.00 to kill, that is. Sync can be detected with a single transistor but it is tricky. A PIC can analyze a composite sync signal and recognize the various parts. If the transistor is an NPN, connect the emitter to ground and couple positive-sync video to the base through a capacitor. DC bias for the base is supplied through a large resistor so the transistor is cut off all the time except during the sync pulses. Take the output from the collector with a pull-up resistor. The circuit is an overdriven, marginally biased amplifier with no feedback. Look at the diagram for most any fairly old TV and you'll see this is how it was done. The trick is to get the video level, bias level, and capacitor values all right so that the transistor only conducts during sync and not video. Often a small capacitor with a resistor in parallel is placed in series with the video signal. This network improves the edges of the sync by high-pass filtering. _____________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com Or call Juno at (800) 654-JUNO [654-5866]