To overcome the problem wherein it is not easy to check that a poor fit caused between a connection edge of an adapter and a connector of a computer is just a poor fit between the connection edge and the connector.

GND pins at both ends of the connection edge 4 of the PCI adapter 1 are connected to cathodes of LEDs 2 and 3. When the PCI adapter 1 is mounted on a computer, the LEDs 2 and 3 enable an easy check for the poor fit between the connection edge 4 of the PCI adapter 1 and a computer connector from outside a bracket 5.