Which device is used to disconnect a power source before maintenance?

The Lockout-Tagout (LOTO) device is specifically designed for safety during maintenance work on equipment or machinery. It serves as a critical safety protocol that ensures a power source is effectively disconnected and cannot be accidentally re-energized while maintenance is being performed. The LOTO process involves placing a lock on the energy-isolating device and tagging it with information regarding the maintenance work being done, which communicates to others that the equipment is out of service and should not be turned back on until maintenance is complete.

This process protects workers from hazardous energy releases, making it an essential practice in maintaining workplace safety standards. Other options listed, such as an auto-reset circuit breaker, surge protector, and transformer, do not fulfill this specific function of isolating energy for maintenance tasks; they serve different purposes such as protection against electrical surges or voltage transformation. Hence, the LOTO device is the most appropriate choice for ensuring safety during maintenance activities.