What is the feature of a fire protection system that may alternatively be an alarm check valve?

A fire protection system may include an alarm check valve, which serves several important functions, one of which is to monitor and report the flow of water within the system. The check valve is integral to ensuring the system maintains its integrity and prevents backflow while also providing the capability for an alarm system to be activated under certain conditions, such as in the event of a fire or system malfunction.

This feature allows water to flow in one direction only, essential for the proper operation of fire suppression systems, including sprinklers and standpipes. When water flows through the valve, it can trigger an alarm to notify occupants or emergency services about the activation of the fire protection system, enhancing safety measures.

In the context of other options, a flow meter is specifically designed to measure the flow rate of water but does not serve the dual function of an alarm system. A test valve allows for system testing without disrupting overall flow but lacks the backflow prevention characteristic; it primarily serves maintenance purposes. An isolation valve is utilized to isolate sections of the system for maintenance but does not involve monitoring flow or activating an alarm. Thus, the check valve stands out as the correct answer due to its dual functionality in both flow control and alarm activation within a fire protection system.