A cartridge is engageable with a medical device, the cartridge comprising an ordered arrangement of N electrical components (540) each with different respective values of an electrical property, and an ordered arrangement of N conductors (522, 524, 526) operably coupled to the ordered arrangement of the N electrical components. A medical device is arranged to receive a cartridge and comprises for each of N conductors on the cartridge, at least a first respective contact arranged to electrically couple with the corresponding conductor when the cartridge is engaged with the medical device the medical device also comprises an evaluation means operable to evaluate the different respective values of an electrical property of N electrical components on the cartridge, wherein the N electrical components form an ordered arrangement which is operably coupled to the N conductors on the cartridge, and a switching arrangement operable to selectively electrically couple a respective pair of contacts to said evaluation means.
