<Yes, relays are a lot slower than electronic devices, and yes, they may <be less reliable. But they're not as slow as all that. They are reliable, especially the sealed ones...saves extracting bugs(moths) with tweezers(aka: Lt Hopper). Speed; the problem is cascade. I've worked with relay trees of good size and while each can do 10s of repetitions persecond tens of them in cascade can only complete one cycle in a second. To do logic like a counter using relays is slow even though the individual relays may be fairly fast. Though using s stepper relay is faster than chained relays. Allison