This page implements a DTMF keyboard/tone generator, and a DTMF tone
decoder.
DTMF (Dual Tone Multi-Frequency)
signalling is the technic used to transmit numbers and some symbols
over the voice frequency band on a telephone line. It's the tones
heard when a number is dialled, or when pressing buttons to navigate
through a call center's menus over the phone. It's also part of the
56k dial-up routine as explained
here.
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The left-hand side of the page lets you generate DTMF tones via
the on-screen keypad. It shows the digits and symbols entered so
far and offer an option to replay them in a row.
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The right-hand side of the page listens to any sound produced by
the left-hand side, and tries to detect DTMF tones in it. It
appends any numbers detected in an output field, and shows
soundwave and frequency visualisations, because why not. It
appends any numbers detected in an output field, and show
soundwave and frequency visualisations, because why not.