An electronic add-on device (200, 300) adapted to be mounted on a receiving device, comprising: - electronic circuitry, - a power source, - a switch arrangement comprising a first switch (335, 345) and a second switch (336, 346), wherein: - the switch arrangement has a first state in which: - the first switch is open and powered, and - the second switch is closed and un-powered, - the switch arrangement has a second state in which: - the first switch is closed and un-powered, and - the second switch is open and powered, characterized in that - the switch arrangement has an intermediate state in which: - the first switch is closed and powered, and - the second switch is closed and powered, wherein: - the electronic circuitry is arranged to detect, with the switch arrangement in the first state, when the first switch is closed, and subsequently change the state of the second switch from un-powered to powered, thereby shifting the switch arrangement to the intermediate state, - the electronic circuitry is arranged to detect, with the switch arrangement in the intermediate state, when the second switch is opened, and subsequently change the state of the first switch from powered to un-powered, thereby shifting the switch arrangement to the second state, - the electronic circuitry is arranged to detect, with the switch arrangement in the second state, when the second switch is closed, and subsequently change the state of the first switch from un-powered to powered, thereby shifting the switch arrangement to the intermediate state, and - the electronic circuitry is arranged to detect, with the switch arrangement in the intermediate state, when the first switch is opened, and subsequently change the state of the second switch from powered to un-powered, thereby shifting the switch arrangement to the first state, the electronic add-on device further comprising a stationary portion and a moving portion, wherein: - the first switch comprises a first stationary switch point arranged on the stationary portion and a first moving switch point arranged on the moving portion, - the second switch comprises a second stationary switch point arranged on the stationary portion and a second moving switch point arranged on the moving portion, and - the moving portion can be actuated from a first state through an intermediate to a second state corresponding to the switch arrangement first, intermediate and second states. - electronic circuitry, - a power source, - a switch arrangement comprising a first switch (335, 345) and a second switch (336, 346), - the switch arrangement has a first state in which: - the first switch is open and powered, and - the second switch is closed and un-powered, - the first switch is open and powered, and - the second switch is closed and un-powered, - the switch arrangement has a second state in which: - the first switch is closed and un-powered, and - the second switch is open and powered, - the first switch is closed and un-powered, and - the second switch is open and powered, - the switch arrangement has an intermediate state in which: - the first switch is closed and powered, and - the second switch is closed and powered, - the first switch is closed and powered, and - the second switch is closed and powered, - the electronic circuitry is arranged to detect, with the switch arrangement in the first state, when the first switch is closed, and subsequently change the state of the second switch from un-powered to powered, thereby shifting the switch arrangement to the intermediate state, - the electronic circuitry is arranged to detect, with the switch arrangement in the intermediate state, when the second switch is opened, and subsequently change the state of the first switch from powered to un-powered, thereby shifting the switch arrangement to the second state, - the electronic circuitry is arranged to detect, with the switch arrangement in the second state, when the second switch is closed, and subsequently change the state of the first switch from un-powered to powered, thereby shifting the switch arrangement to the intermediate state, and - the electronic circuitry is arranged to detect, with the switch arrangement in the intermediate state, when the first switch is opened, and subsequently change the state of the second switch from powered to un-powered, thereby shifting the switch arrangement to the first state, - the first switch comprises a first stationary switch point arranged on the stationary portion and a first moving switch point arranged on the moving portion, - the second switch comprises a second stationary switch point arranged on the stationary portion and a second moving switch point arranged on the moving portion, and - the moving portion can be actuated from a first state through an intermediate to a second state corresponding to the switch arrangement first, intermediate and second states.