A connector in a fixed location is a jack and a moveable connector is a plug. The distinction is relative, so a portable radio is considered stationary compared to the cable from the headphones; the radio has a jack, and the headphone cable has a plug. Where the relationship is equal, such as when two flexible cables are connected, each is considered a plug. Jacks use the reference designator prefix of J and plugs use the reference designator prefix of P. It is possible in the case of box mounted connectors for the connector to be a receptacle with male pin contacts. In this case the connector is designated a jack (J ref des) regardless of the contact gender because the housing for the contacts is in fact configured as the receptacle even though its mate (the plug) goes around the receptacle. See MIL-STD-38999 and similar cases.