To prevent a system from being broken by including a pull-up control circuit pulling up a female contact, a printed circuit board insertion detecting circuit generating a control signal, a power supply control circuit cutting off connection to a power supply terminal, and a bus connection control circuit cutting off connection to a bus signal terminal.

This device involves a conductive contact Ba 5 and a conductive contact Bb 6 at the positions next to both ends of a printed circuit board edge of a printed circuit board 1, and is connected to a ground terminal B 15 of the printed circuit board 1. In case that the printed circuit board 1 is inserted properly, a contact Aa 3 is provided at such a position as the contact Ba 5 and a contact Aa 3 come into contact with each other. In case the printed circuit board 1 is inserted in a connector 2 properly, a contact Ab 4 is provided at such a position as it comes into contact with the Bb 6. It is thus possible to prevent the printed circuit board from being broken due to the printed circuit board not being inserted deep, enough.