Reprinted from The Fabricator:
"Recognizing these limitations, the Occupational Safety and Health Administration (OSHA), the American National Standards Institute (ANSI), and other performance standards-making organizations support the use of the latest product concepts and designs for movable machine guard safety interlocks and systems.

These include:
1) Tamper resistance.
2) Positive-opening, normally-closed (NC) contacts.
3) Positive-guided relays.
4) Control reliability.
5) Self-checking, safety circuit monitoring and control modules (also called “safety relay modules”).

Each is aimed at heightening the level of safety for the machine operator/maintenance personnel when they open machine guards that expose them to hazardous areas.

By their design, they provide manufacturers with a means of creating safer workplaces, meeting legal requirements, and reducing the risk of liability.