Which type of device confirms the operational state of sprinkler systems?

The supervisory device is designed to continuously monitor the condition and operational state of various components within a sprinkler system. It provides real-time feedback on the system's readiness and can alert personnel to any issues that may arise, such as a malfunctioning valve or a change in the pressure within the system. This allows for quick identification and resolution of potential problems, ensuring that the sprinkler system remains functional when it is needed most.

Waterflow alarm devices are primarily used to alert when the water begins to flow through the system, indicating a potential activation of the sprinkler heads in response to a fire. While they indicate that the system is operational at that moment, they do not provide continuous monitoring of the system's overall state like supervisory devices do.

Pendent sprinklers are a type of sprinkler head that disperses water directly downward but do not have any role in confirming the operational state of the entire system.

A system riser is a vertical pipe within the water distribution system that allows water to flow into the piping network, but it does not confirm the operational state of the sprinkler system. Thus, the supervisory device stands out as the correct answer.