For the truly paranoid worried about chips or a defeat cheat, you
could mount a spring loaded plunger on the top, where the plunger hit
the switch, and the switch would allow the plunger to 'overrun' a bit.

You'd have to insert the key into the top, push up a bit to gain
clearance for lip on the bottom, set the key into the recess on the
bottom.

This would keep chips from jamming the switch, and a defeat piece
would have to be purpose-built.
Too long, it won't go in, too short, it won't push the top plunger up
to trip the switch.

That's a lot more work, though!


Dave

geeez - if you really want to be "secure", just embed an RFID in each chuck
key, and a reader on the machine - if the machine's own key isn't in the
holder then .... and if a "foreign" ID is detected, machine won't start
until the guy from security comes with the safety guy and a triplicate form
and they get the computer guy to assign a new key ID to the machine ....


** Posted from http://www.teranews.com **