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
We present an efficient DTMF detection algorithm based on the
non-uniform discrete Fourier transform that meets all of the
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
This version is nearly identical to the final printed version.
Last Updated 09/24/99.