A system (102) comprising a box (104) for implanting in a mammal body part (106), which box is provided with a first electrical contact (110, 121, 114, 116, 118, 120), and a module (108) for accommodating in the box, which module is provided with a second electrical contact (122, 124, 126) for cooperation with said first electrical contact. The first electrical contact and the second electrical contact are mutually movable, at least in a stationary accommodation of the module in the box, between a contact position in which said first and second electrical contacts are electrically connected, and a non-contact position in which said first and second electrical contacts are separated from each other.