The OMRON D4NL-4AFG-B is a Guard Lock Safety Door Switch from the D4NL Series. It is a compact, electromagnetic locking type safety interlock switch designed for hinged or sliding machine guards that require recessed mounting capability and redundant lock monitoring (3 NC) . This model features 1 NC + 1 NO contact configuration for the door detection circuit (slow-action, direct opening mechanism on the NC contact) and a separate 3 NC contact configuration for the solenoid lock monitoring circuit.