What must be done before performing maintenance on a 120V AC system?

Turning off the power is essential before performing maintenance on a 120V AC system for safety reasons. Electrical systems can present serious hazards, including electrical shock or short circuits, if touched while they are live. By ensuring that the power is turned off, a technician minimizes the risk of injury and allows for a safer working environment.

Additionally, it is a standard safety procedure to confirm that all circuits are de-energized before starting any work. This step not only protects the technician but also safeguards the equipment being serviced, preventing potential damage that could occur from accidental electrical contact. It's vital that safety protocols, such as turning off power, are strictly adhered to when working with electrical systems.