Extender activates additional chime when the doorbell rings. Chime plugs into any standard wall socket. Transmission range up to 100 feet. Adjustable volume control. Dimensions: 3.5" w x 1.375" d x 5.125" h - chime 2" w x 0.625" d x 6" h. 3 sounds, Westminster, Ding-Dong and Ding. 75 decibel maximum. UL/cUL, FCC and IC Certified.