Optional accessory for use with the HomeAware Main Unit (sold separately) Once linked to the HomeAware Main Unit, alerts you to video relay service (VRS), fax, or incoming call from a telephone located in another room (NOTE: the HomeAware Main Unit comes packaged with a telephone cord enabling user to receive alerts from landline phone located in close proximity to the main unit) Plugs into standard telephone wall jack, fax machine jack, or phone jack associated with VoIP or VRS systems Uses (2) #357 silver oxide batteries (included) and already installed into bottom of unit