System Sensor HGRL-LF Low Frequency Compact SounderLow Frequency Sounder notification appliances meet the NFPA 72 2010 2013 low frequency requirements for all commercial and certain residential sleeping spaces. The Sounders provide Temp 3, Coded, Continuous, and now provide Temp 4 which meet the NFPA 72 2010 2013 low frequency requirements as well as the NFPA 720 2012 carbon monoxide low frequency requirements. Studies driving these requirements have shown that a lower frequency is more effective at