A signal transmission system comprising an interface circuit (100, 101) and a transmission line, the interface circuit comprising: a signal line having signal, auxiliary and connection nodes defined therealong, the connection node connected to the transmission line; signal-handling circuitry (120, 121) connected to the signal line at the signal node so that an effective capacitance of the signal-handling circuitry (120, 121) is experienced at the signal node; an auxiliary circuit connected to the signal line at the auxiliary node so that an effective capacitance of the auxiliary circuit is experienced at the auxiliary node; a signal pair of inductors (15, 25) connected along the signal line adjacent to the signal node and at either side of the signal node; and an auxiliary pair of inductors (35, 45) connected along the signal line adjacent to the auxiliary node and at either side of the auxiliary node, wherein: the signal pair of inductors (15, 25) are configured to have a mutual coupling defined by a coupling coefficient kS; the auxiliary pair of inductors (35, 45) are configured to have a mutual coupling defined by a coupling coefficient kA; for each said pair of inductors (15, 25, 35, 45), the inductors of the pair are arranged such that a current flowing along the signal line in a given direction through one of those inductors induces a current flowing along the signal line in the same direction in the other one of those inductors given a positive coupling coefficient; and kS has a positive value and kA has a negative value. a signal line having signal, auxiliary and connection nodes defined therealong, the connection node connected to the transmission line; signal-handling circuitry (120, 121) connected to the signal line at the signal node so that an effective capacitance of the signal-handling circuitry (120, 121) is experienced at the signal node; an auxiliary circuit connected to the signal line at the auxiliary node so that an effective capacitance of the auxiliary circuit is experienced at the auxiliary node; a signal pair of inductors (15, 25) connected along the signal line adjacent to the signal node and at either side of the signal node; and an auxiliary pair of inductors (35, 45) connected along the signal line adjacent to the auxiliary node and at either side of the auxiliary node, wherein: the signal pair of inductors (15, 25) are configured to have a mutual coupling defined by a coupling coefficient kS; the auxiliary pair of inductors (35, 45) are configured to have a mutual coupling defined by a coupling coefficient kA; for each said pair of inductors (15, 25, 35, 45), the inductors of the pair are arranged such that a current flowing along the signal line in a given direction through one of those inductors induces a current flowing along the signal line in the same direction in the other one of those inductors given a positive coupling coefficient; and kS has a positive value and kA has a negative value. the signal pair of inductors (15, 25) are configured to have a mutual coupling defined by a coupling coefficient kS; the auxiliary pair of inductors (35, 45) are configured to have a mutual coupling defined by a coupling coefficient kA; for each said pair of inductors (15, 25, 35, 45), the inductors of the pair are arranged such that a current flowing along the signal line in a given direction through one of those inductors induces a current flowing along the signal line in the same direction in the other one of those inductors given a positive coupling coefficient; and kS has a positive value and kA has a negative value.