Is there anything I can use these for?

4n30   =  NPN Darlington Output
4n35   =  NPN Transistor Output

Thanks!
Arn C.

Mikko Heilin had a schematic for a 4N35-based octave-up unit.  Can't seem to find it on my work machine at the moment, but I believe Mikko is reachable over the net.

Thanks Mark!  I will try a search!
Peace!
Arn C.

I'm very interested in it too!!!
If you find a schem could you post it too me? I've got some 4n35 among all my recycled components...
I'm wondering if these kind of components can replace LED/LDR units.

I've found nothing yet.  Anyone else know what these can be used for?

Thanks!
Arn C.

I´m not sure but there are some nice simple MIDI thru or MIDI signal repeat (multi output) box circuits that can be made with common optoisolators. If you need those. And I am not sure if that type of opto works in this kind of circuit.

Maybe a electrically safe interface for switching power for your gear or stage lightning? I read an E.C interwiev and he told about his Pete Cornish stuff and I remember he had something footpedal push button that was named "Amps On". That would be cool.

I havn't tried it, but those simple envelope follower wahs that work by having a transistor as the variable frequency determining component, might work with one of those transistor sections.
But I doubt that they would replace a led/ldr combo, because not symmetric on the output (but, maybe two units, the diodes in series and the transistors back to back in parallel?? some experimenting to be done there..)