A method of verifying that a first unit and a second unit being mounted to each other are correctly paired, the first unit comprising a first visual identifier and the second unit comprising a second visual identifier, the method comprising the steps of (i) capturing an image of the first and second unit mounted to each, the image comprising both the first and the second visual identifier, and (ii) processing the captured image to (a) identify the first and the second visual identifier, and (b) determine whether the captured identifiers represent a predefined combination of visual identifiers to thereby verify the pairing.
