NEIEP Mechanics Practice Exam

Interlocks are safety devices designed to ensure that certain conditions are met before a system can operate. In the context of systems that involve doors, such as elevators or industrial machinery, interlocks send signals to the controller based on the status of those doors.

When the doors are closed and locked, it indicates that the system is safe to operate. This state guarantees that there are no obstructions and that personnel are not at risk of being exposed to moving parts. The controller relies on this signal to allow the operation of the machine or elevator, as it confirms that it is safe to proceed.

In contrast, signals indicating that the doors are open and unlocked, in maintenance mode, or malfunctioning all serve to alert the controller of unsafe conditions, thereby preventing operation until the issues are resolved. Each of these conditions represents a potential safety hazard that would require the system to be inactive until it is safe to continue.