A method for identifying among a plurality of devices, through which a voice communication path is connected, a device transmitting an echo signal onto the voice communication path, includes transmitting a predetermined signal to each of the devices from a predetermined portion on the voice communication path, receiving a response signal for the predetermined signal from each of the devices, measuring a period of time for the predetermined signal to travel from the predetermined portion to each of the devices and for the response signal to travel back to the predetermined portion, monitoring a upstream signal and a downstream signal traveling on the voice communication path, extracting an eco component from the downstream signal to determine an echo delay time, and comparing the period of time and the echo delay time to determine a device which causes the echo signal.
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