ECHO CANCELLATION CIRCUIT

PROBLEM TO BE SOLVED: To realize impedance matching with high accuracy while also reducing work load during impedance matching.SOLUTION: When adjusting the matching of a hybrid circuit H, an adjustment signal transmission unit AS sends out an adjustment signal Sa in place of a transmission signal Ss. When adjusting the matching, a residual echo detection unit ED detects a residual echo level pertaining to the adjustment signal Sa included in a received talk signal which has been outputted from an echo canceller EC. When adjusting the matching, an impedance matching adjustment unit IMA switches over a plurality of matching circuits Z1-Zn provided in the hybrid circuit H and used for impedance matching purpose to sequentially select one, acquires a residual echo level detected by the residual echo detection unit ED for each of the matching circuits Z1-Zn, and selects one of the matching circuits Z1-Zn whose residual echo level is smallest as a matching circuit for an analog telephone line L.