Some Fatar Keybeds have used a conducting spring that can come into contact with two conducting rails as a keyswitch. Since the spring is used as an electrical contact, it is advantageous to gold-plate it to prevent corrosion. Paul Vandervoort's personal Janko also uses this technology. While these switches (like rubber dome switches) can fail over time, periodic application of the following product has been found to be a good fix:
http://www.stabilant.com/sizes01h.htm
The switch is usually arranged with two rails such that the spring goes from contacting the top rail to contacting the bottom rail. The top of the key movement acts like a normally close switch, and the bottom of the key acts like a normally open switch. Since rubber membrane keyswitches use two normally open switches, the scanning circuitry is typically NOT interchangeable between rubber membrane and spring keybeds.
In some designs the spring switch doubles as the return spring for the key.
