Clearly, a standard doorbell will not function effectively when in the home of a deaf person. However, there are a variety of products available for deaf people to use in the place of traditional doorbells. These products use light and vibration–and loud sounds for those who are not entirely deaf–in helping to alert a deaf person that someone is at the door.
Light doorbells, or visual alerting devices, use light to alert a person that someone is at the door. These doorbells range from a single light connected to the doorbell to a more elaborate system that flashes all the lights in the house. These doorbells are either activated by a doorbell button or a door knock alert system. With a door knock alert system, when someone knocks on the door a vibration sensor unit detects the vibration caused by the knocking and thus signals a bright light to flash. The vibration sensor is usually adjustable on a door knock alert system, so the level of vibration that triggers the alert is determined by the person using it.
For someone who is not entirely deaf but can't hear a regular doorbell, a loud doorbell might be the answer. Loud doorbells send out increased audio throughout the house or apartment which alert the person that someone is at the door. Like Light doorbells and door knock alert systems doorbells, loud doorbells are generally wireless devices. They are also probably the most affordable option of deaf-oriented doorbell.