The Omron D4SL-N4GFA-DN is a guard lock safety-door switch with a mechanical lock and 24 VDC solenoid release, indicated by an orange LED. The built-in switch configuration is 3NC + 1NC/1NO, giving you three normally-closed safety contacts plus one auxiliary contact that can be wired NC or NO. The head is resin, the conduit outlet is M20, and the connection method is a connector.
The 24 VDC solenoid release means this switch unlocks the guard when power is applied to the solenoid — a standard fail-locked configuration. The orange LED confirms solenoid power is present, which helps during commissioning and fault-finding on the line. The 3NC + 1NC/1NO contact arrangement is typical for safety circuits: the three NC contacts go into the safety relay or controller (redundant channel monitoring), while the auxiliary contact signals the guard status to a PLC or indicator lamp. The M20 conduit entry accepts standard metric cable glands, and the connector version (N in the code) means you can pre-wire a harness and plug it in during installation — saves time on panel builds or machine changeovers.
This class of guard lock switch is used on machine guarding — access doors, gates, and hatches where the hazardous motion must be stopped before the guard can be opened, and the guard must stay locked until the machine is safe. The solenoid release (power-to-unlock) is the standard choice for applications where a power loss should keep the guard locked, not release it. The resin head and M20 conduit make it suitable for industrial environments with moderate washdown or dust exposure.