The MSM7603/7603B is an improved version of the MSM7602 with basically the same configuration, and offers twice the cancelable echo delay time of the MSM7602. The MSM7603B I/O interface allows switching between μ-law PCM and A-law PCM. The MSM7603/7603B is a low-power CMOS IC device for canceling echo (in an acoustic system or telephone line) generated in a speech path. Echo is canceled, in digital signal processing, by estimating the echo path and generating a pseudo echo signal. When used as an acoustic echo canceller, the device can cancel the acoustic echo, between the loud speaker and the microphone, which occur during hands free communication such as on a cellular phone or a conference system phone. When used as a line echo canceller, the device can cancel the line echo which returns due to impedance mismatching in a hybrid. In addition, a quality conversation is made possible by controlling the level and by preventing howling through a howling detector, double talk detector, attenuation function and a gain control function, and by controlling the low level noise by means of a center clipping function. The use of a single chip CODEC, such as the MSM7704 (3 V) and MSM7533 (5 V), allows an economic and efficient echo canceller to be configured.