what is the best site to know capacitive keyboard & Mercury Switch keyboard and its Working Principles?

Question

with figure.

Answer 1

The capacitive switch uses capacitor technology to implement a switch. Two plates are mounted at the bottom of the switch. The plunger has a third plate at its base, which makes contact with the two plates at the bottom of the switch when the plunger is depressed. An AC signal is applied to one fixed plate and is sensed on the other fixed plate when the plunger is depressed and completes the circuit.

With a Mercury Contact Switch, Two contacts are enclosed in a small flexible tube, which is filled with a small amount of mercury. When the plunger is depressed, the flexible tube is compressed and causes the mercury to short with the two contacts, completing the circuit. They have low contact resistance and less contact bounce than contact switches.

The source page I've included has this detailed description with illistrations towards the bottom of the page. Hope this helps!