I could never describe it very well myself - just a cool old effect box. LOL How's that? [img]images/smilies/icon_mrgreen.gif[/img]
Actually, I was looking them up on ebay tonight, and
this link will take you to a page where the seller really describes them in detail. There's some downloadable wav files that you can listen to as well.
Dunno if you have Jeff's Guitar Shop album, but you can hear it used as a subtle effect on the lead part of "Two Rivers" there. It gives it a kind of warbly, distorted sustain the way he uses it on that particular track. Jeff has used them off an on for years. If you're a Floyd fan, you'll see what I meant about thinking Gilmour used one from listening to those sound clips. The more extreme sound effects in the clips remind me of a lot of sounds on "Wish You Were Here"