a housing comprising a first receptacle to which a first target apparatus is configured to be detachably attached by sliding the first target apparatus in a sliding direction;

a first electrical apparatus-side terminal configured to be electrically connected with a first target apparatus-side terminal of the first target apparatus attached to the first receptacle;

a first terminal cover configured to move between a covering position at which the first terminal cover covers the first electrical apparatus-side terminal and an exposing position at which the first terminal cover leaves the first electrical apparatus-side terminal exposed; and

a first locking member configured to engage with the first terminal cover positioned at the covering position, and configured to move between a lock position at which the first locking member restricts movement of the first terminal cover from the covering position to the exposing position and an unlock position at which the first locking member does not restrict the movement of the first terminal cover from the covering position to the exposing position,

wherein the first locking member is configured to move from the lock position to the unlock position while the first target apparatus is slid in the sliding direction to be attached to the housing, and

when the first locking member is positioned at the lock position, a user is unable to directly shift the first locking member from the lock position to the unlock position.