A non-lock detector switch is provided on or near an adapter to be switched by a connector plug when the connector plug with memory function unit is coupled to the adapter having an antenna for accessing to the memory function unit. Accordingly, connection state of each connector can be directly and simultaneously detected by the switching operation of the detector switch at a time preceding a little from a time when the antenna detects the memory function unit just having closed to a position opposed to the antenna. This is useful for exactly and detecting without delay the complete coupling state of each one of a number of adapters in distinction from the incomplete coupling state of any one of adapters.