A patch bay is an assembly of hardware so arranged that a number of circuits, usually of the same or similar type, appear on jacks for monitoring, interconnecting, and testing circuits in a convenient, flexible manner. Circuits are traditionally connected with short patch cords, though, in some implementations, computers are used to make the connections and handle numerous, instantly recallable configurations.
Patch bays are used at installations where it is necessary to connect and reconnect various hardware devices, for example at technical control facilities, patch and test facilities, at telephone exchanges, broadcast studios, and recording studios.
Note 1: Patch bays facilitate flexibility in the use, routing or restoration of a variety of circuit]] types, such as dc, VF, group, coaxial, equal-level, and digital data circuits.
Source: from Federal Standard 1037C and from MIL-STD-188.