An interface circuit for a switch array having an array of switches, each closeable to couple a row conductor of a plurality of row conductors to a column conductor of one or more column conductors, comprises a current generator and a current detector. The current generator has a plurality of row interface ports for coupling to different ones of the row conductors and is arranged to generate a switch array current for coupling to the row interface ports, the switch array current having a different one of a plurality of different switch array current magnitudes for different ones of the row interface ports, and generate one or more reference currents each having a different reference current magnitude. The current detector has one or more column interface ports for coupling to the one or more column conductors and is arranged to detect the switch array current flowing at any one of the one or more column interface ports, and generate a row indication indicative of which of the row conductors a closed one of the switches is coupled to by determining which one of the switch array current magnitudes the detected switch array current has by comparing the detected switch array current with the one or more reference currents.