Byron Wireless Doorbell Set, Portable Battery-powered Chime & Plug-In White\nProduct Details\n--Install your wireless chime system easily: both the button and the mobile chime are battery-powered. The second chime simply plugs into the socket of your choice. No wiring is required.\n--Plug in the chime on the ground floor. The mobile chime will accompany you anywhere in the house and you won't miss a single visit.\n--Choose from 16 melodies and adjust the volume to suit your needs (5 levels, up to 80-85 dB). An indicator light on the button tells your visitor that the doorbell has been activated.\n--The waterproof wireless doorbell button runs on a CR2032 button cell battery (included, life: 3 years). The mobile chime uses 3 AA batteries (not included).\n--The chimes communicate with the doorbell button via radio frequencies (433 MHz, open field range: 150 m). Expand your system by adding up to 6 buttons, on the back door, for example.