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Which electrically operated waterflow alarm initiating device is inserted into the riser above where the water supply enters the building?
Pressure switch
Vane-type switch
Flow switch
Check valve
The correct answer is: Vane-type switch
The vane-type switch is the correct choice for this question because it is specifically designed to detect the flow of water in a fire protection system. These switches are installed in a position where they can monitor the movement of water directly, which typically occurs above the water supply entry point into a building's riser. When water begins to flow, the vane mechanism is activated, sending a signal to alert the fire alarm system. In contrast, a pressure switch is generally used to monitor the pressure within the system rather than the flow of water. It helps ensure that adequate pressure is maintained but does not provide immediate detection of water movement. A flow switch, while it may sound similar to the vane-type switch, refers to a different mechanism that operates by detecting changes in flow rather than directly interacting with the movement of water like the vane type. Similarly, a check valve is a mechanical device designed to allow water to flow in one direction while preventing backflow; it does not serve the purpose of alarm initiation, as it does not have an electrical output to signal an alarm system.