Edwards 520 Hz sounder bases add UL 464 listed low frequency audible output to the entire Edwards line of intelligent smoke, heat, and CO detectors. When mounted with a matching detector, they provide a clean finished appearance and high performance audible output. The integrated appearance of combined detector and base offers a low-profile and unobtrusive alternative to separately installed horns and detectors. It also reduces installation costs by requiring only one electrical box and one wiring run. Edwards low frequency sounder bases can operate as independent local alarms, or as part of a zone or system alarm with synchronized audible output. The SB4U-LF base provides low frequency sounder capability to V-Series and FX-Series smoke detectors. All sounder bases match the finish of compatible devices, and the sound output slots complement the air entry openings of the detector. The end result is a compact unit with an attractive appearance.