FIELD: communications engineering. SUBSTANCE: echo suppressor uses adaptive filter for evaluating echo signal created by unknown echo channel. Evaluated value of echo signal is subtracted from return signal to eliminate echo signal created by unknown echo channel. In order to prevent false convergence of echo suppressor to signal incorporating tones only, provision is made for system and method for detecting tones in absence of other frequencies. Values across adaptive filter taps are filtered off to obtain filtered signal. Energy in filtered signal is compared with that in non-filtered values across filter taps to determine tones only. In presence of tones only echo suppressor is not enabled to reduce adaptive filter spacing. EFFECT: eliminated false convergence resulting from reception of tones only in input signal. 23 cl, 5 dwg
