- Source: Extension bell
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.
Further reading
Telephone and Telegraph Engineers' Handbook. BiblioBazaar. 2008. pp. 274–276. ISBN 978-0-559-36662-8.
References
External links
"Shop Notes / Method of connecting a bell to a telephone". Popular Mechanics. Hearst Magazines. March 1906. p. 333. Retrieved 25 October 2009.
This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 22 January 2022.