Boogie type switching circuits w/optocoupler & relay

[six el six]

I am trying to understand how these thing work and I'm searching the net for a circuit I can build to get a better handle on these circuits so that I can troubleshoot them better.

I see Doug's post on it but I'm trying to find a circuit to build that has both a relay and an optocoupler so that I can see better how they're supposed to operate.

Does anyone have a suggestion on where to start?

[jojokeo]

Usually when switching on higher AC voltage 24v relay from a lower voltage DC source using an optocoupler it also involves a triac in combination.