Abstract: Improved isolation between the four-wire receive and transmit ports in a four wire-to-wire converter in a communication system is obtained by utilizing a tapped delay line network in an active hybrid circuit. The active hybrid circuit includes a first amplifier which terminates the four-wire receive channel in its characteristic impedance, amplifies the four-wire received signal, and excites a resistor network that terminates the two-wire channel in its nominal characteristic impedance. A second amplifier and a resistor circuit function as a weighted summer for nulling the received four-wire signal with the signal passing through the resistor network to obtain signal cancellation at the four-wire transmit port when the four-wire receive channel is activated. The tapped delay line network may be connected either between the first amplifier and resistor network or between the first amplifier and the received four-wire signal input of the second amplifier.