Abstract: A modular connector comprises an insulative housing that accepts an RJ-45 style jack from its front, and a molded insert from the opposite side. Each molded insert includes a signal conditioning circuit that provides a proper electrical coupling between a physical interface device (PHY) or encoder/decoder and an unshielded twisted pair (UTP) cable to a high speed computer network. Such signal conditioning comprises a common mode choke for each of the transmitter and receiver circuit pairs that are constructed from twin-lead transmission line sections. Each common mode choke comprises two stiff wire conductors that are brought together at a uniform critical separation distance for a critical longitudinal run length. The wire size, surrounding dielectric, separation distance, and run length are all controlled to arrive at a common-mode choke equivalent with series inductance, transformer coupling, and capacitance values suitable for use with 100BASE-T Fast Ethernet and 1000BASE-T Gigabit Ethernet.