the kitchen has a card register?? to register new students' dinner swipe cards. Its suddnely stopped working but im struggling to work out if its a problem with the server or the device itself.

It is a COM device that is basically a grey block that has a power plug attached to it and a cable to the com port. there are rather helpfully no lights on it to tell you the thing is switched on and working, and it doesnt make any noise either.

So does anyone know of a way i can test to see if the device is actually working because i think i am right in saying if you unplug it windows will still list it as a com device in device manager and wont alert you that the device isnt present?

Can anyone suggest anything to try before we buy a new one, although ive no idea what they are even called or where they are sold!