The MURS Chime is an auxiliary chime that can be connected to the M538-BS transceiver, or any other entry alert receiver. The chime module connects to the N/O relay output on the base station and will play one of three tunes (Westminster chime, London Bridge or Oh my Darling) when the base station receives a signal from the MURS Alert transmitter. The chime has an adjustable volume and operates on 2 "AA" batteries(not included).