Abstract: A double talk detector for echo cancellers monitors the ratio of four wire transmit in energy to transmit out energy (ERLE), along with the change and direction of change of an estimated impulse response, to control updating of the estimated inpulse response. When the ERLE is low and the directional change of the impulse response is high, indicating an end path switch, the double talk detector enables the estimated impulse response to be updated. If the directional change of the impulse response and the ERLE are both low, indicating the occurrence of double talk, the detector inhibits updating of the impulse response until either the ERLE becomes sufficiently high, indicating single talk, or the directional change of the impulse response becomes sufficiently large, indicating an inconverged state of the canceller. The arrangement allows convergence of the echo canceller to be properly controlled both in response to double talk and to changes in the impulse response of the end path.