What is one way ELS can be activated electrically?

The activation of the Emergency Lighting System (ELS) can occur through a switch located in the Flight Deck, which allows the crew to change its status from armed to on. This is particularly important during emergencies when visibility is compromised, ensuring that essential areas in the aircraft are illuminated for safe evacuation or operations.

The switch in the Flight Deck provides pilots with manual control over the ELS, enabling them to respond to specific situational needs promptly. The decision to activate emergency lighting is often critical in guiding crew members and passengers safely through the aircraft during an emergency evacuation.

The other methods listed, while potentially related to power sources or alert systems, do not provide the tactical control that the Flight Deck switch does in terms of immediate activation of the ELS. Making the move from armed to on status effectively puts the system into action as required in an emergency situation.