This standard details an interface protocol, including a general message architecture and specific message sets, for communications between a CCTV switching sub-system and an Access Control sub-system. This standard may be applied to any two or more sub-systems of either type. This standard may also be applied to sub-systems of other types if their functionality is supported within the message sets. This standard assumes bi-directional communications where no sub-system is a master over the other/s. Each sub-system may issue any of the defined messages, however, each sub-system may decline requests that are made from the other. This standard is intended for use by manufacturers in the design of CCTV, Access Control, and other similar systems in the security industry and related industries. It is also intended for reference by all affected parties, including security system installers and programmers, system specifiers, security managers and other end users.