Interlock switches without guard locking detect whether a guard is in place but do not hold it shut — when the guard opens, the safety output drops and the machine should stop. Selection comes down to contact configuration, coding method (to prevent defeat), and the mechanical layout of the guard.
Specs to confirm before ordering:
- Switch technology: mechanical (tongue-and-key actuator), magnetic (coded reed), RFID-coded non-contact, hinge-mounted
- Coding level: uncoded, low-coded, high-coded (uniquely coded RFID for defeat resistance)
- Number of safety contacts (typically 2 NC + 1 NO is standard)
- Performance Level capability — PL d typical, PL e with proper wiring and monitoring
- Approach direction (linear, hinge, multi-direction for mechanical types)
- Actuator style: tongue/key (mechanical), magnet (magnetic), coded target (RFID)
- Cable or M12 connector style, pin count
- IP rating — IP65 standard, IP67/IP69K for washdown
- Series-wiring capability if multiple switches share one safety relay input
Common gotchas: mechanical tongue-and-key switches are easy to defeat by removing the key and inserting it directly into the switch — high-coded RFID switches resist this and meet higher defeat-resistance categories under ISO 14119. Magnetic switches will trigger on any matching magnet, which is why "high-coded" types use unique target-switch pairings. Series wiring of multiple safety interlocks reduces diagnostic coverage and can drop the PL rating; modern systems often use safety inputs on a controller instead of series-wired contacts. Actuator alignment matters — a misaligned tongue actuator wears out or fails to engage reliably.
Typical applications: machine guard monitoring on milling machines, mixer access doors, robotic cell gates without active locking requirement, and small-machine perimeter guards. For applications requiring the guard to stay locked while the hazard is present, see the Interlock Switches with Guard Locking category.
For obsolete interlock switches, send the OEM part number for a sourcing quote.
