Patent ID: 7480262

Claim:
A telephone terminal for use in a telephone system equipped with a main device for performing a line exchange and a plurality of telephone terminals which are connected to the main device via cable lines, transmit a voice signal to the main device and receives it transmitted from the main device to acoustically reproduce it, comprising: a receiving detector which detects a signal level of a receiving voice signal incoming from the main device; a transmitting detector which detects a signal level of a transmitting voice signal to transmit it to the main device; an adjustment device configured to adjust the transmitting voice signal; and a controller which obtains a control value capable of switching a communication state from a receiving state to a transmitting state to make an acoustic echo to be added to the transmitting voice signal be minimum, based on each a detection result of the receiving detector and a detection result of the transmitting detector, and controls the adjustment device based on the control value.