on the left side of the io board most of the small connectors are inputs what you have is a sinking logic, basically you have to take a ground wire and short it to one of the inputs and you should see the diagnostic change from say one to zero the input address can be found out by using the diagnostic page the input addresses i believe start with 1000 on the diag page the top left bit would be 0 and 1 would be next going down so say #1000 would be tool changer in and #1001 would be tool changer out there are more inputs and the second page but i cannot remember what number they start with. there is more info in the service manuals. you may also be able to use he m-fin. you can basically wire as many inputs as you want to the m fin in parallel and check for the m fin before doing to the next line. so if the pallet comes down and the switch changes state the pallet clamped. if m fin does not cycle then alarm. good luck
REYTECH Machine Service Corp. CNC repair NY, NJ
http://www.reytechmachine.com