Hi All
Way back I seem to remember seeing a circuit in some book or other that acts like a resistor but can be changed using only electronic means. Was supposed to replace the volume pot in a amplifier I think.
Question 1 : Is it possible to "emulate" a resistor in this way?
Question 2 : Is it possible to "emulate" a capacitor as well?

Now the big question : If both the above are possible, does anyone have a circuit for each that is nice and simple (and stable).

Reason: I still like the 555 timer idea but dont want to have a whole bunch if resistors and caps to get it working. If there is a way to "create" the values I need, lets get the PIC to do the hard work. I'll worry about the display later.

Best