Which component alerts the fire department during a fire alarm?

The flow switch is responsible for detecting the flow of water in a sprinkler system during an alarm condition, indicating that water is being released to suppress a fire. When a flow switch is activated by the movement of water, it sends a signal to the fire alarm panel. This panel is typically connected to the fire department's notification system, which alerts them of the fire alarm activation.

The flow switch is a critical component in the fire protection system, as it directly communicates the presence of a potential fire condition due to the discharge of water from the sprinklers. This prompt notification is essential for the fire department to respond quickly and effectively.

In contrast, other components like the pressure gauge measure the pressure within the system and provide important information for maintenance, the alarm bell emits an audible alert but doesn't directly notify the fire department, and the control valve is used to manage water flow in the system, but it doesn’t have a role in alerting emergency services. Understanding the specific function of each component reinforces the importance of the flow switch in the overall fire alarm response system.