Hey! Thanks for the response. So, are you indirectly saying that those with the "optoisolators on the control input side" are preferred rather than incompatible? I know that the Arduino's have female pins opening for the GPIO and RP's have the male. My mind naturally gravitates to the idea that they...

Basic question, seems obvious, but I've been wrong before.

Will relays advertised for Arduinos compatible with Raspberry Pis?

I don't want to waste any money while I'm learning this stuff.

Thanks.