Silent X10 Mod (cheap SSR)

I’m feeling a bit retro for the holidays, so here’s another classic: If you’ve got a non-dimming X10 switch, you’ve experienced the incredibly loud, obnoxious sound that it makes when you switch it on or off. (Mine’s in my stairwell) There’s a simple mod to silence the thing: remove the triac relay and replace it with a solid state relay. SSRs are a bit expensive, running at least $10 each last time I checked. [Willis Dair] realized that he could build his own, inexpensive SSR with an optoisolator and an alternistor(AKA Triac). The resulting circuit runs about $3 in parts.