The D4SL-N2HDA-D is a guard lock safety-door switch from Omron, built for interlocking access doors on machinery where the door must stay locked until the hazardous motion stops. The 'A' in the code means mechanical lock with 24 VDC solenoid release — power to the solenoid unlocks the door, so a loss of power keeps it locked (fail-safe). The switch block is 3NC + 2NC, giving you three normally-closed safety channels and two normally-closed monitor contacts for the control circuit. Metal head (D) and a G1/2 conduit outlet (2) make this variant suited for environments where the switch takes mechanical abuse and the wiring runs through a standard metric/PF conduit. Connection is via terminal block inside the housing, so no special tooling needed on site.
The 24 VDC solenoid release (orange LED indicator) tells you the coil voltage and gives a visual status — the LED is on when the solenoid is energized (door unlocked). That LED is a quick diagnostic for the panel builder or field tech: no light means the door is locked and the solenoid circuit is dead, which is the safe state. Standard release key (metal) means the actuator key is a metal tongue that mates with the switch head. The metal head and metal key together handle repeated door cycles without wearing out the engagement point. If you're replacing a switch on a guard door that cycles hundreds of times per shift, the metal construction matters for longevity.