Escher sketch sync?

Hello. How do you know that Escher Sketch is synced ? Wich one of the two RCA is the sync input ?
thx

You can use either jack, as described in the user reference card.
https://github.com/lzxindustries/documentation/tree/master/Escher%20Sketch

Yes, thanks.
But whats the special behavior of ES when sync, because i see no difference with the rca pluged in or not.

Further explained here: