Schneider Electric FFS06728020 is a loop-powered base sounder from the Apollo Intellia ESI-20 series, with integrated short-circuit insulator and adjustable sound output of 55-91 dB. The white housing measures 115 mm in diameter and 38 mm in height, sitting under a compatible Apollo detector on the addressable fire-alarm loop. Used for local audible signalling in commercial and industrial fire-detection systems.