PURPOSE: To enable econimization by setting the element value of a source equivalent circuit corresponding to the constitution of a two-line/four-line conversion part, calculating a filter coefficient by converting the source equivalent circuit to a specified impedance function, and deriving a cancel signal by a digital filter using the obtained filter coefficient.

CONSTITUTION: The element value of the source equivalent circuit is set by an element value set part 26 and converted to the impedance function of a (z) function by the bilinear conversion of an over sampling frequency at an impedance function calculation part 25. Coefficient calculation parts 21 and 22 calculate the and a digital balancing circuit arithmetic part 19 calculate the filter coefficient by substituting this impedance function to a transmission function. On the other hand, transmission coarse gain set information and reception coarse gain set information for controlling the gains of coarse gain control circuits 12 and 13 is applied to a plane gain calculation part 18 and according to the coarse gain control of the coarse gain circuits 12 and 13, level control is executed to cancel a crosstalk component. Thus, economization is enabled.