At 11:06 AM 23/02/99 -0000, Jezz Brookes wrote: >I want a circuit that you can vary the gain from +1 to -1 (i.e. inverting) Horowitz and Hill, "The Art of Electronics" 2ed page 253, figure I. That's what I use when I want to adjust modulation from + through zero to -ve. paul perry Frostwave P/L Melbourne Australia