DTMF
Dual-tone multi-frequency — the pair of audio tones a telephone keypad produces on a button press, so a receiving system can identify exactly which button was pressed.
Standardized internationally under ITU-T Recommendation Q.23 (the tones) and Q.24 (detection), DTMF pairs one low-group and one high-group frequency so a genuine keypress is essentially never confused with a stray sound. It remains the backbone of secure phone-based payment collection industry-wide, decades on, precisely because a tone is unambiguous where voice recognition has to interpret sound into meaning.
A caller pays by card at the end of a pickup order. Once the payment step starts, the system stops parsing ordinary speech and instead watches for the tone pairs the keypad produces as the caller enters card number, expiration, and security code — then returns to normal conversation once the charge confirms.
The most consequential mistake is assuming any number spoken or entered during a call gets treated identically. It doesn't: an ordinary spoken number becomes part of the call the way any sentence does, while a card number entered through the secure DTMF step is deliberately isolated from that same record.
Card and PIN digits, keyed or spoken, take a completely separate path from the rest of a call and never enter the transcript, recording, or database — the fuller mechanism on Payments.
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