TUCoPS :: Phreaking Caller ID :: russ-aon.wav

AONs (Automatical Number Identifiers). This signal is most interesting of all. When you pick up the receiver of the ringing phone you can hear beautiful chord in the first 500 milliseconds. It is a 7- digit number of the calling party represented by CCITT tones without silence between the tones. If you have a microprocessor-equipped phone it can decode tones and show the calling party number on a LCD display. In some cases the phone must send a short 500 Hz request tone before the CO equipment plays the chord. In fact this signal was designed for identification of the calling party by the toll office. But advanced amateurs guessed how to use this feature in the first self-made computerized phones in the middle 1980's. Those phones, called AONs (automatical number identifiers), was spread first among the computer underground. Later they filled a black market, and only lasted a few years before the Telcos officially permitted to use AONs.

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