Installs in minutes! Sounds whenever the door opens. Up to 150-ft Operating Range. Plays bell, chime or music. 32 selectable codes block interference from outside signals. Transmitter uses 6-volt battery (included and installed). Transmitter is installed to door jamb. Mount magnetic piece to door. Plug door chime into any 110V electrical outlet within operating range. Plays six sounds. 21/4″ speaker for realistic sound. High/low volume control.