Abstract: This invention relates to adaptive digital filters for echo cancellation in a bi-directional data transmission channel. Substantial hardware savings for a digital adaptive filter are possible, if hardware structures for performing filter operations are shared. In a digital adaptive filter with resource sharing filter operations are performed sequentially with a limited number of hardware structures. This invention discloses a digital adaptive filter with resource sharing with further hardware savings (FIG. 3). Corresponding to a characteristic decrease of the magnitude of the filter coefficients for echo cancellation, a first and second filter computation means (4.sub.A, 4.sub.B) are connected to a coefficient storage means (3) with a different bit width to receive coefficients (c.sub.0, c.sub.1 . . . c.sub.N/2-2, c.sub.N/2-1 ; c.sub.N/2, c.sub.N/2+1 . . . c.sub.N-2, c.sub.N-1) having different magnitudes and/or a first and second coefficient adapting means (7.sub.A, 7.sub.