What is the effect of phase 1 service on elevator operation during a fire alarm?

The correct understanding of the effect of phase 1 service on elevator operation during a fire alarm involves its design to restrict elevator accessibility to ensure safety. When phase 1 service is activated, it prevents the elevator from responding to new calls, meaning that it will not service any floors. This is crucial in a fire emergency, as elevators represent a potential hazard; they could inadvertently serve floors in danger or become unusable due to fire conditions.

This mechanism is part of a broader safety protocol that directs elevators to a designated floor, typically the ground level, so that they can be utilized by emergency response teams without the risk of interference from regular building occupants moving in and out of the elevator. Thus, under phase 1 service, the primary focus is on restricting access and prioritizing safety rather than maintaining normal passenger use.

Other answer choices suggest different functionalities that do not align with the specific goal of phase 1 service. For instance, powering off all elevators entirely or sending them to the ground floor involves different operational protocols that may or may not apply based on a building's fire safety system. Normal passenger operation is directly contradictory to the purpose of phase 1 service, which is to prioritize safety during emergencies.