Adding Composite Sync signal to an STF

[Colleton]

I recently saw someone on facebook mention that he'd added something called a compsynch signal to his ST (I'm assuming it was an STF).  I'm including the pic he posted below.

 

What exactly does this do?  I have a silkscreen outline for these components on my STF.  Not sure what the resistor values should be though?  Pretty sure the transistor is a 2N3904 and the crystal diodes are IN914.  So idf I add these components to my STF will I have composite video output?

[Colleton]

I know I'm being ignorant and am begging your forbearance.  From what I can find there is no such thing as composite synch?  Just a composite signal generated by the RF Modulator.

 

Am I at least right in thinking that the resistor values are (left to right):  100 ohm, 150 ohm, and 10K ohm?

 

Thanks!

[snarkdluG]

Here you go.

[Colleton]

Thank you. tf_hh had filled me in on this on facebook, but this was a more in-depth explanation. 

 

I have the parts on order.  Going to give it a try on my STF with a scart cable and OSSC.

[Colleton]

Thanks for the help everyone.  I got the necessary parts in this past weekend and have modded both of my STF machines.  Both now work with my composite SCART cable via my OSSC, whereas both had no display with the same cable/OSSC combo before the mod was done.