Here is a very simple but extremely useful little circuit. It is a touch sensitive key or keyer, small enough to build into a rig.
Only a few components are used (not a capacitor in sight!).
Duplicating the circuit can form the basis of a touch sensitive iambic keyer.
For the touch paddles I used two brass buttons.
Note
To operate one finger or part of the hand needs to be 'earthed'. In practice, I use the paddles built into a box with my K1EL keyer. Of course, if a metal container is used, the touch pads (buttons) have to be insulated from the case.
I built mine in an ABS box with a compartment for a 9v battery. I used a strip of self adhesive aluminium strip as the 'ground' or 'earth', placed so the hand is in contact with it during keying.
As it is tiny, it can be included in your rig, thus making the idea useful for portable work and one less item to pack!
Current is up to 4ma if 15v is used, less of course if a lower voltage is employed.
Try it - it is brilliant!