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Sounders
Low Frequency Sounders
A sounder is the audible-only counterpart to a horn, and in System Sensor's line the term marks 520 Hz low-frequency appliances built for sleeping areas under NFPA 72. Two-wire SpectrAlert Advance models (HR-LF red, HW-LF white) run on 12 or 24 V circuits for wall or ceiling installation, and L-Series models (HRL-LF, HWL-LF) bring the lower current draw and universal mounting plate of the newer line, with ceiling (HCRL-LF, HCWL-LF) and compact single-gang (HGRL-LF, HGWL-LF) versions.
Where a strobe is needed in the same location, ceiling low-frequency sounder strobes (PC2RL-LF, PC2WL-LF) combine both functions. All models produce the square-wave 520 Hz tone in a Temporal 3 pattern and synchronize with other appliances on the circuit, which matters in corridors where several devices are in view.
Wall sounder strobes are under low frequency, and standard-tone horns under horns. Browse the full System Sensor catalog, or contact our team for help with sleeping-area layouts.
