1) Telephony equipment
Found on
https://www.crosswordclues.com/clue/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 ...
Found on
http://en.wikipedia.org/wiki/Extension_bell
No exact match found.
