Doorbell

Doorbell
This article is about auditory signals for doorways. For the type of computer interrupt, see Interrupt#Doorbell.
Antique shop doorbell
Ornate doorbell in Venice

A doorbell is a signaling device typically placed near a door. Most doorbells emit a ringing sound to alert the occupant of the building to a visitor's presence, when the visitor presses a button. Many modern doorbells are electric — they are actuated by an electric switch. The electric doorbell was invented by Joseph Henry in 1831.[1]

Most people use their index finger to push a door bell, but young people who have grown up with text messaging are more likely to use their thumb.[2]

Contents

Doorbells

Wired system

In most wired systems, a button, located around the height of the doorknob, activates a signaling device (usually a chime, bell, or buzzer) inside the building. This single-pole, single-throw (SPST) switch momentarily closes the doorbell circuit. One terminal of this button is wired to a terminal on a transformer. A doorbell transformer steps down the 120–240-volt AC electrical power to a lower voltage, typically 10–20 volts. The transformer's other terminal connects to one of three terminals on the signaling device. Another terminal is connected to a wire that travels to the other terminal on the button. If there is another button (typically near a back door), it is connected between the transformer and the third terminal on the signaling device. The transformer, being energized constantly, does consume a small amount (about 1 to 2 W) of standby power constantly,.[3][4]

Most signaling devices consist of two solenoids and two flat bars. The flat bars are tuned to two pleasing notes. The flat bars are mounted loosely above and below the solenoids. When the doorbell button is pressed, the first solenoid's plunger strikes the bottom bar. When the button is released, a spring on the plunger pushes the plunger up, causing it to strike the other bar. If the other bell is used, it will activate the other solenoid, which will strike only one bar — typically the bottom bar.

More elaborate signaling devices play a short musical tune, such as Westminster Quarters.

The deaf use visual signaling devices — typically light bulbs — rather than audible signaling devices.[5][6]

Circuit diagram

Doorbell.JPG

Wireless system

A button near the door activates a built-in transmitter. The transmitter sends a radio signal to the doorbell radio receiver inside the building. When the radio signal is detected by the receiver, it activates the doorbell. In larger metropolitan cities, a trend has developed over the past decade that uses telephone technology to wirelessly signal doorbells as well as to answer the doors. In many cities throughout the world, this is the predominant form of doorbell signalling.

See also

References

  1. ^ Bachman, Frank P. (2006). Great Inventors and Their Inventions. Yesterday's Classics. p. 78. ISBN 1-599-15066-2. http://books.google.com/books?id=rBDTCtKSWfkC&pg=PA78. , Extract of page 78
  2. ^ "Why your thumbs are getting bigger!". CBBC Newsround. 25 March 2002. http://news.bbc.co.uk/cbbcnews/hi/sci_tech/newsid_1892000/1892881.stm. Retrieved 2010-07-29. 
  3. ^ "Why Did President Bush Suddenly Start Talking about Standby Power?", presentation by Alan Meier, this is a cool device. http://www.energystar.gov/ia/partners/prod_development/downloads/power_supplies/PSPresent2.ppt
  4. ^ MISCELLANEOUS ELECTRICITY USE IN U.S. HOMES Marla C. Sanchez, Jonathan G. Koomey, Mithra M. Moezzi, Alan Meier and Wolfgang Huber, LBNL Berkeley CA, http://www.osti.gov/bridge/servlets/purl/795945-9c8LM1/native/795945.pdf
  5. ^ "Alerting and Communicating Devices for Deaf and Hard of Hearing People — What's Available Now". Clerccenter.gallaudet.edu. http://clerccenter.gallaudet.edu/InfoToGo/418.html. Retrieved 2011-09-27. 
  6. ^ "NPR — At Gallaudet, a Turn Inward Opens New Worlds". Npr.org. http://www.npr.org/templates/story/story.php?storyId=5369960. Retrieved 2011-09-27. 

External links


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Look at other dictionaries:

  • doorbell — n. a bell or other sounding device, actuated by a push button at an outer door; the push button activating the bell; alos, the ringing of such a bell; as, I was in the shower and didn t hear the doorbell. Syn: bell, buzzer. [WordNet 1.5] …   The Collaborative International Dictionary of English

  • doorbell — c.1815, from DOOR (Cf. door) + BELL (Cf. bell) …   Etymology dictionary

  • doorbell — [n] chime buzzer, door knocker, ringer; concepts 74,284,529,685 …   New thesaurus

  • doorbell — ► NOUN ▪ a bell in a building which can be rung by visitors outside …   English terms dictionary

  • doorbell — [dôr′bel΄] n. a mechanism, now usually activated by a push button at the entrance of a building or room, that rings, buzzes, etc. to alert the occupants of a visitor …   English World dictionary

  • doorbell — noun VERB + DOORBELL ▪ press, ring ▪ answer ▪ He refused to answer the doorbell. ▪ hear DOORBELL + VERB ▪ …   Collocations dictionary

  • doorbell — n. to ring a doorbell * * * to ring a doorbell …   Combinatory dictionary

  • doorbell — UK [ˈdɔː(r)ˌbel] / US [ˈdɔrˌbel] noun [countable] Word forms doorbell : singular doorbell plural doorbells a button near the front door of a house that you press to make a sound to tell the person in the house that you are there …   English dictionary

  • doorbell — 1. noun a) A device on or adjacent to an outer door for announcing ones presence. It can be mechanical, directly sounding a bell, or a button that electrically sounds a chime or buzzer inside the building. b) A button that actives an electric… …   Wiktionary

  • doorbell — door|bell [ˈdo:bel US ˈdo:r ] n a button outside a house that makes a sound when you push it so that people inside know you are there ring the doorbell (=push the button) …   Dictionary of contemporary English

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