The
keyboard lock is a little lock on the front of most
computer cases, that when locked will allow no input from the keyboard. It's one of those little locks much like the kind found on
vending machines; the round ones with the cylindrical keys that all look the same. They can be found on
AT and previous cases,
ATX cases no longer have the Keyboard lock, it died with the
turbo button.
The lock is a normally open
switch. When locked it closes a connection between two pins on the
motherboard. It's easy enough to bypass; just pop off the case and unplug the switch.
In recent years the usefulness of the keyboard lock has diminished, due to operating systems that depend more on the
mouse than the
keyboard. But in the days of
command line interfaces, a keyboard lock was a rather useful
security feature, provided nobody could get inside your case.
I recently discovered another type of keyboard lock. My keyboard started sticking, so I replaced it with an old keyboard from my
derelict parts bin. It has a small plate in the upper left corner, marked with what I assume is the name of the manufacturer. After a little poking and prodding, I noticed that when enough pressure is applied to the very top edge of the plate, it pops right off. Just underneath is a small
slide switch, that when switched upwards, locks the keyboard.
I find this
secret alternative very useful. People who try to use my keyboard think it's locked through conventional methods. But unplugging the switch from the motherboard will do them no good.