> I understand that some common (ie: typically used for on/off signals)
> opto-isolators can work for linear signals.  Anyone here know if this
> is true

It is true. For example, I was looking at a project a couple of days
ago for a cordless drill speed control, for a drill which didn't have
one, obviously. The on/off trigger now breaks the beam of an opto-
interrupter to a greater or lesser extent, the resultant receiver voltage
controlling the speed

> or have another way to do this?

Possibly a VCO driving the opto's LED. You might try a CMOS
gate oscillator in which the frequency varies, or a 555 in which the
duty cycle varies. Some analogue systems - eg IR headphones -
use a similar analogue -> digital -> analogue scheme

Joe
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.