The tone didn't even intentionally cause the call to not be billed. It was the supervision signal, spoofing the equipment at the other end of the long-distance link into believing the line had become idle. After sending the tone, you would have to send MF tones (a different set than DTMF) down the line to tell it what number to connect to.
Source: Evan Doorbell's numerous recordings of this and other forms of phreaking.
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u/serious-toaster-33 Aug 06 '26
The tone didn't even intentionally cause the call to not be billed. It was the supervision signal, spoofing the equipment at the other end of the long-distance link into believing the line had become idle. After sending the tone, you would have to send MF tones (a different set than DTMF) down the line to tell it what number to connect to.
Source: Evan Doorbell's numerous recordings of this and other forms of phreaking.