Funkgong HX: Wireless bell set with acoustic and visual signaling (flashing light). The transmitter has a range of up to 200 meters and can be mounted outdoors. It is suitable for connection to existing doorbell systems. There are 8 melodies and 256 self-learning frequencies available. Distance extender HX: By linking multiple HX wireless distance extenders, you can achieve an unlimited range for the HX wireless bell sets and HX receivers.