System Sensor B200SR-LF-WH Retrofit Low Frequency Sounder BaseThe System Sensor B200SR LF WH is a low frequency sounder base for Select Series plug in detectors, providing 520 Hz audible notification for sleeping areas that require NFPA 72 compliant low frequency signaling. It is compatible with Select Series intelligent detectors and B501BH style NAC circuits for retrofit applications, with tone (Temporal 3 or Continuous) selected locally by jumper. It mounts to a wide range of junction boxes for both new and