Get alerted to visitors at your door with this alerting notification system. This alerting device works by simply attaching the Bellman Visit Door transmitter near an existing doorbell, chime unit or intercom. When activated, the transmitter sends a radio signal to the Bellman Visit receiver with which it is paired. Choose how to be alerted from flashes, sounds and vibrations. This alerting system works for mechanical/electrical doorbells and intercoms. Great for the deaf and hearing impaired.