Abstract: An erroneous insertion prevention mechanism of connectors is provided for preventing the erroneous insertion between engagement fixed tables provided on both ends of a cable and engagement sections provided on the devices or units by changing the shapes and installing positions thereof. The erroneous insertion prevention mechanism of connectors comprises engagement fixed tables of an engagement connector, engagement fixed tables of an engagement connector, guide rings and manually screwing screws, guide rings and manually screwing screws respectively mounted on both ends of the cable, wherein the shapes of the engagement fixed tables are differentiated from each other and they are provided at the positions where they are displaced from the center of the engagement connector.

Abstract: A mechanism for fixing a printed circuit board to a case has a guide support portion and a stopper. The guide support portion guides the printed circuit board in a direction of insertion and pulling out of the printed circuit board and supports the printed circuit board. The guide support portion is disposed in the case. The stopper engages with the printed circuit board which is inserted into the guide support portion, and fixes the printed circuit board to the case.