To provide an echo compensating means in a nonlinear type communication system.

An echo compensator 34 and an echo attenuation element controlling a sound echo and a line echo are certified as effective in a fixed network when an echo signal correlates to an input signal of a digital filter. In the case echo compensation in a radio telephone set 1 is not appropriate, an echo compensating means has to be provided in, e.g. the radio telephone set or the terminal of a mobile radio network to accomplish satisfactory communication quality in a network in which sound encoding is adopted such as the mobile radio network. According to this, a nonlinear effect in a transmission channel caused by an encoder 11 and a decoder 12 is simulated from existing signals 51, 52 and bfi in a transcoder unit 36 by using a component element 33 to which a nonlinear communication system is known, and a known echo suppressing means can be executed.