An extension bell or extension ringer is a device that generates a sound to indicate an incoming telephone call, but is not included in a telephone set itself.
Extension bells may be louder than ordinary telephone ringers. As such they may be used by persons with moderate hearing impairment to help them detect incoming telephone calls, especially when they are outside the telephone's room.
The devices were in use by the late 19th century. An early Australian system at Mount Crosby, Queensland featured an extension bell which was connected to an engineer's telephone over a distance of a quarter mile.
- Telephone and Telegraph Engineers' Handbook. BiblioBazaar. 2008. pp. 274–276. ISBN 978-0-559-36662-8.
- "Telephone extension ringers". Australian government - Job Access. Retrieved 25 October 2009.[dead link]
- "Hearing / ROHIs". City Council of Devon, United Kingdom. Retrieved 2009-09-04.
- "Today". The Brisbane Courier. 27 August 1891. p. 5. Column 1.
- "Shop Notes / Method of connecting a bell to a telephone". Popular Mechanics. March 1906. p. 333. Retrieved 25 October 2009.
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