A media processing device includes: a housing; a cover rotatable between open and closed positions; a main logic board (MLB) supporting a controller, and having a slot extending into the MLB from an open end at a perimeter of the MLB, the slot traversing the MLB from an upper surface to a lower surface; a receiver affixed to the MLB on a first side of the slot, and an emitter affixed to the MLB on a second side of the slot, to emit radiation detectable by the receiver; and a tab movably coupled to the housing, to obstruct the slot and prevent detection of the radiation by the receiver when the cover is in a first one of the open and closed positions, and to clear the slot and permit detection of the radiation by the receiver when the cover is in the other of the open and closed positions.