A housing is configured to receive a plug that includes an upper face, a lower face, and a front face. The housing also includes a cutout portion that traverses the upper face and the lower face, opens to the front face of the housing, extends for a length of the plug, and is formed in a direction of insertion of the plug. An opening is configured to receive the plug, which is formed on the front face of the housing and connected to the cutout so that a plug is received by the opening. A distance from the upper face to the lower face of the housing is approximately equal to a diameter of the plug.