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DTMF Frequency vs DTMF Codes | DTMF Signal Frequencies and Codes

This page on DTMF Frequency vs DTMF Codes mentions DTMF Signal Frequencies and DTMF Signal Codes.

The DTMF stands for Dual Tone Multi Frequency. The DTMF signalling is used in local access network where transmission path between transmitter and receiver is 2-wire analog subscriber line. This signalling is used in telecommunication network from one end to the other end.

DTMF Frequencies

The figure depicts standard touch tone frequencies along with keys or codes. One touch generates two frequency tones to be transmitted on the transmission line. This is shown by rows and columns.

When "*" key is pressed, it generates 941 Hz and 1209 Hz simultaneously. The table below mentions DTMF frequencies e.g. "low group frequencies" and "high group frequencies" for each of the DTMF codes.
Refer Pulse Dialing vs Tone Dialing >>.

High Group Frequencies (Hz)
1209 1336 1477 1633
Low Group Frequencies (Hz) 697 1 2 3 A
770 4 5 6 B
852 7 8 9 C
941 * 0 # D

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