1-800-400-1540 Alertmaster AM-DX Door Announcer by Ameriphone, item 01882 Works with Alertmaster to notify you when someone knocks at your door or when an intercom buzzer or doorbell sounds.. $49.95 plus s&amp;h. Buy 2 on same order = $47.95 ea.
(someone; knocks; at your door) (an intercom buzzer or doorbell; sounds; )
someone an intercom buzzer or doorbell
knocks sounds
at your door