Which of the following can be considered as a supervisory signal initiating device?

• A. Low air pressure switch
• B. Water level indicator
• C. OS&Y valve with a normally open switch
• D. Pressure gauge

Answer: (C)

Supervisory signals monitor the status of protective-system components and alert when something isn’t in the required state. An OS&Y valve equipped with a normally open switch is a classic supervisory initiating device because the valve position is critical to the system’s readiness. The switch changes state as the valve moves, sending a supervisory signal to the fire alarm control panel to indicate the valve is not in its proper position. This focused monitoring of a key component makes it the best example of a supervisory initiating device.

A low air pressure switch, while it can indicate an abnormal condition, is more about monitoring pressure in a system rather than specifically supervising a critical valve’s position. A water level indicator and a pressure gauge provide readings or trigger alarms under certain conditions but do not inherently initiate a supervisory signal in the same direct way as a valve-position switch.