Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · Protective devices and interlocks

Safety switch (interlocking device)

Also known as: safety interlock switch, guard interlocking switch

German: Sicherheitsschalter

In machine safety, a safety switch is a position switch used as an interlocking device on a movable guard, detecting whether the guard is closed and, in versions with guard locking, holding it closed. ISO 14119 sets requirements for its design, selection and defeat prevention.

  • Machine safety
  • EU

In one sentence

A safety switch detects whether a movable guard is closed and signals the control system so hazardous functions cannot run with it open.

Example

The access door of a robot cell has a coded safety switch with guard locking; the robot can only move in automatic mode when the door is closed and locked.

How it applies

  • Types: ISO 14119 distinguishes interlocking device types by actuation principle and coding, from uncoded mechanical switches to high-coded RFID switches. Coding level influences the measures needed against defeat.
  • Engineering: Mechanical safety switches use positive opening contacts, so the contacts are forced apart when the guard opens. Switch type, mounting and fault masking in series connections affect the achievable PL.
  • Defeat prevention: Designers must assess the motivation to defeat and choose mounting, coding and additional measures accordingly, see Tamper resistance.
  • Documentation: Document the switch type, coding level and mounting requirements. The documentation team should state in the manual that bypassing a safety switch is prohibited and describe how to proceed after a switch fault.

Safety switch vs. disconnect switch

In US usage, safety switch can also mean an enclosed disconnect switch for isolating electrical power. That device serves Energy isolation and lockout, not guard interlocking. Use the qualified term to avoid confusion.

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: ISO 14119, Safety of machinery — Interlocking devices associated with guards — Principles for design and selection

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Blog and are not part of any standard.

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