Keystone jacks are mounting receptacles used in data communications, particularly local area networks (LANs).
The jack is usually mounted in a wall plate or patch panel.
A keystone plug is the matching male connector, usually attached to the end of a cable or cord.
A principal advantage of keystone connectors is their versatility.
Several types of keystone jack can be mounted on a single patch panel.
They are available in unshielded and shielded forms and can accommodate cords and cables having various numbers of conductors.