Extension bells may be louder than ordinary telephone ringers.
2.
Eventually, electronic telephone ringers became the norm.
3.
It also has a telephone ringer as its horn, so instead of a honk, it rings!
4.
These avoid the need to generate 20Hz 90V sinusoidal AC, but are not compatible with standard telephone ringers.
5.
Buzzers were not usually designed to accommodate the 90-110 volt, 20 30Hz ringing signal used by telephone ringers.
6.
Central-office powered ringers continue to function and by designating one telephone ringer per line it is possible to identify the line that is ringing.
7.
Following a 1975 ruling which permitted third-party devices to be connected to phone lines, manufacturers began to produce accessory telephone ringers which rang with electronic tones or melodies rather than mechanically.
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