In this paper we propose a computationally simple algorithm for the de
tection of a sinusoidal tone for applications in the held of telecommu
nication systems. More specifically, we have developed an algorithm ba
sed on fuzzy logic (FL) to disable an echo canceller in a telephone ex
change. The Fuzzy Tone Detector (FTD) presented uses three simple time
-domain parameters and a matching phase based on only three fuzzy rule
s, trained by a new hybrid learning tool. A fuzzy system called a Fuzz
y Phase Reversal Detector (FPRD) was also trained for the detection of
phase reversals. The new algorithm outperforms the traditional method
s in terms of robustness to channel noise, working up to a signal to n
oise ratio (SNR) of 0 dB. (C) 1998 Elsevier Science Inc. All rights re
served.