Other, optional, sub-standards are defined to allow enhanced performance, e.g. H.243 provides for multipoint control function, i.e. when two or more sites conference there is provision for sending signals through a Multipoint Control Unit (MCU). H.281 provides for far-end camera control from the local site, H.282/H.283 provide the requirements for remote control of devices other than the camera, and T.120 provides for data exchange.