Low Frequency Audible Signal The GHLF Series low frequency audible signal is a high-quality, low profile, audible appliance that offers a dependable 520 Hz square wave audible alarm with industry low current draw. The GHLF is ideal for any occupancy that requires low frequency notification appliances. The GHLF horn offers a temporal 3 tone with a jumper selection to choose between normal or loud decibel levels. A temporal 4 pattern is also available when used with the Gentex GTSM Synchronization Control Module. The GHLF is shipped with a die cast metal mounting bracket which incorporates the popular Super-Slide® and Checkmate® feature. The GHLF horn is listed to ANSI/UL 464 and CAN/ULC listed.