Potter's ADDRESSABLE LOW FREQUENCY SOUNDER BASE has an independent sounder module that may be programmed as a single station, zone, or all-call sounder. It supports Class A, Class X, and Class B wiring and does not require an SLC loop address. 6". 24 VDC. Meets NFPA 72 Low Frequency Signal Requirements and UL 464 Audible Signaling Devices.