Hi,
I wonder if they are fast optocouplers in 4-pin DIP packages. I know PC817 and equivalents, they are 4 us typ. I'd like to look at dual, triple and quad units too as long as they are pin compatible with 4-pin units stacked together (like PC827? PC837 etc.)
It's all about pin compatibility (direct replacement in someone's else bad design). I already know many parts for indirect replacement, no, I do not need more