Which engineering control is operated by a key or computer code, and when disabled (key or code removed), the laser cannot be operated?

• A. REMOTE OPERATION
• B. WARNING SYSTEMS
• C. MASTER SWITCH CONTROL
• D. NOMINAL HAZARD ZONE (NHZ)

Answer: (C)

The concept here is a lockout-style engineering control that physically prevents the device from operating without authorized access. A master switch control is designed so that the laser can only be turned on if a key is inserted or a code is entered. When the key is removed or the code is not provided, the switch is opened or disabled, and the laser cannot be operated. This creates a fail-safe barrier that stops use unless the appropriate authorization is present, which is exactly how a key- or code-operated control functions.

Remote operation might still work if the system isn’t locked by such a control, so removing the key won’t necessarily disable it by itself. Warning systems alert you to conditions but do not prevent the laser from being used. NHZ is a planning concept about the hazardous zone and exposure, not a mechanism that stops operation.