What must be done before working on electrical systems?

Before working on electrical systems, it is crucial to de-energize the system and utilize lockout/tagout procedures. This step is essential because it ensures that the electrical system is completely safe to work on by disconnecting it from its power source. Lockout/tagout procedures involve physically locking and tagging the power sources to prevent accidental re-energization while maintenance or repair work is being performed.

This practice helps to protect not only the person working on the system but also others who might be nearby. By de-energizing the system, the risk of electric shock or other electrical hazards is significantly reduced. Therefore, these precautions are fundamental to maintaining safety within electrical work environments, making it the correct answer for what must be done before starting work on electrical systems.