A cable driver (301) for driving a single ended transmission medium such as a coaxial cable (115) comprising a core (120) and a shield (121) comprises a differential driver (104, 377) comprising a first output (151) for putting a first signal to the core (120) of the single ended transmission medium (115), a second output (152) for putting a second signal to the shield (121) of the single ended transmission medium (115) through a termination resistor (118) having an impedance close to the characteristic impedance (Z 0 ) of the single ended transmission medium (115), and a third output (153) for putting a transmit ground supply signal (GNDT), local to the differential driver, to the shield (121) of the single ended transmission medium (115) through a first high frequency low impedance path (112). In use, the current through the third output (153) will be substantially the inverse of the common mode current through the first and second outputs (151, 152). Hence both the common mode current and its inverse are provided to the single ended transmission medium (115). They cancel each other out and thus advantageously low EMI emissions occur.