SMPTE RP 139 : 1997

Describes the mechanism for the transfer of control messages between tributaries used within a general-purpose communications channel of an interface system which transports data and digital control signals between equipment utilized in the production, post-production, and/or transmission of visual and aural information. It is intended that the mechanism described in this practice be utilized when transferring control messages between tributaries used as a part of an overall system. The tributaries may be located either within a local network or on separate local networks which are interconnected by means of gateways and an interconnection bus. It is further intended that this mechanism, when used as part of an overall system, shall allow the interconnection of programmable and nonprogrammable equipment as required to configure an operational system with defined functions, and will allow rapid reconfiguration of a system to provide more than one defined function utilizing a given group of equipment.