[sdiy] Vactrols == Optocouplers?

[Peter Grenader]

It was my understanding that an opto-isolater, or opto-coupler is more of a
generic term used  for any device that uses light as an electrically
isolated controller, much like hall-effect devices do with magnetism.  With
that, a vactrol would be considered a type of opto-isolator, but one that
incorporates a photocell resistor.  I wasn't aware that opto-isolators infer
to the use of a photo transistor necessarily.

Am i full of holes with this?

- P