Telephone line signalling

Warning tone

End of period - A tone provided to the paying party for a call to indicate that the period for which payment has been credited will soon expire.

Operator intervening - A tone warning participants in a call that privacy of the conversation has been breached by the intervention of an operator.

Pip tone - A tone provided to the paying party for a call to indicate that expiry of the period for which payment has been credited is imminent.

Recorder warning - A tone warning participants in a call that the conversation is being recorded.

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