IEEE Signal Processing Letters, vol. 5, no. 7, pp. 160-163, Jul. 1998.

Efficient Dual-Tone Multifrequency Detection Using the Nonuniform Discrete Fourier Transform

Matthew D. Felder, James C. Mason, and Brian L. Evans

Department of Electrical and Computer Engineering, Engineering Science Building, The University of Texas at Austin, Austin, TX 78712-1084 USA - -

DTMF Information Page - Non-confidental Disclosure Statement


The International Telecommunications Union (ITU) recommendations for dual-tone multi-frequency (DTMF) signaling are not met by conventional DTMF detectors. We present an efficient DTMF detection algorithm based on the non-uniform discrete Fourier transform that meets all of the ITU recommendations. The key innovations are the use of two sliding windows and development of sophisticated timing tests. Our algorithm requires no buffering of input samples. To perform DTMF detection on n telephone channels, our algorithm requires n MIPS on a digital signal processor (DSP), 120 + 30 n words of data memory, and 1000 words of program memory. Using the new algorithm, a single fixed-point DSP can perform ITU-compliant DTMF on the 24 telephone channels of a T1 time-division multiplexed telecommunications line.

The final draft as submitted to the IEEE Signal Processing Letters is available in PDF - Postscript - GNU-Compressed Postscript formats. This version is nearly identical to the final printed version.

Last Updated 09/24/99.