This part of IEC 60728 describes physical interfaces for the interconnection of signal processing devices for professional CATV/SMATV headend equipment or for similar systems, such as in up-link stations. This standard, in particular, specifies the transfer of MPEG-2 data signals in the standardized transport layer format between devices of different signal processing functions. RF interfaces and interfaces to telecom networks are not covered by this standard. In addition references are made to all other parts of the IEC 60728 series and, in particular, for RF, video and audio interfaces, to IEC 60728-5. For connections to telecom networks, special Data Communication Equipment (DCE) is necessary to adapt the serial or parallel interfaces specified in this document to the bitrates and transmission formats of the public Plesiochronic Digital Hierarchy (PDH) networks. Other emerging technologies such as Connectionless Broadband Data Services (CBDS), Synchronous Digital Hierarchy (SDH), Asynchronous Transfer Mode (ATM), etc. can be used for transmitting MPEG-2 Transport Streams (TS) between remote locations. ATM is particularly suitable for providing bandwidth on demand and it allows for high data rates.