There are two red indicator LEDs between the enabling side and the Triacs which indicate when they are on. The four interfaces are +5v, Ground, and two commanding lines.By
I'm just running 110V AC through this commanded by an Anduino UNO.
But, with this Solid State version, it is ACTIVE HIGH, so a reboot or power outage of the Pi does NOT trigger the relay (which is what I want). This is a great relay and I highly recommend it if the specs fit your needs.By
The relay interfaced nicely with the raspberry pi and seems to work great. Being solid state there's no audible "click" when you trigger the relay which is nice. LED indicators let you know if a particular relay is active or not. I have another SainSmart 5V 2-channel relay (not solid state -[...] and the problem I had with it was that it was ACTIVE LOW (no a defect, but by design). So, whenever my raspberry pi rebooted and the signal on that GPIO pin dropped to LOW, the relay triggered (which is not what I wanted).