1. Circuitry for detecting properties of an accessory removably connected thereto via a multi-pole connector, the circuitry comprising: first, second and third circuit terminals for coupling to respective first, second, and third poles of said connector; an output for providing evaluation values indicative of properties of the accessory; first current sourcing circuitry coupled to said first circuit terminal for providing a first current; a switch network comprising first, second, third and fourth switch network terminals, said first switch network terminal coupled to a reference potential, said second switch network terminal coupled to said second circuit terminal, said third switch network terminal coupled to said third circuit terminal; comparator circuitry comprising first and second input terminals for providing a comparison signal, said first input terminal being coupled to said first circuit terminal; second current sourcing circuitry having a monitor node coupled to said second comparator input terminal and an output node coupled to said fourth switch network terminal for providing a second current to said switch network; at least one of said first current sourcing circuitry and said second current-sourcing circuitry being responsive to a digital control word for varying said first or said second current; and control logic for operatively controlling a state of the interconnections of said switch network, for adjusting said digital control word in response to said comparison signal until a voltage at said first circuit terminal is equal to a voltage at said monitor node, and for supplying said adjusted digital control word associated with the state of the interconnections to said output as an evaluation value.