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3. SIGNALLING
The exchange provides sound signalling by different tones and rings to
make easier of subscribers calling.
Tones on extension
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Dial tone - long tone
The exchange is ready to receive dialling.
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Busy tone - short tone repeatedly
Called extension is busy or feature is refused
.
▬█▬█▬▬▬▬▬█▬█▬
Ringing extension´s tone – 2 long tones and
space repeatedly
Called extension is ringing .
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Ringing trunk´s tone – long tones and space
repeatedly
Calling from public line.
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Ringing door intercom´s tone - long, short,
long tone repeatedly
Ringing, notice from door intercom.
