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This article introduces the various relay platforms available for the domestic TV market. Digital TV signals Television pictures invariably start life as digital video signals. Three separate sets of data represent the red, green and blue components of the scene being televised. The typical required bandwidth for each programme depends on the picture quality as shown alongside. The various programmes can then be combined for distribution within the home as terrestrial multiplexes or on satellite transponders, or the data can be “packetized” for distribution using recognised techniques. UHF and Satellite Freeview programmes can be distributed at their incoming frequencies on a coaxial DTT network for display on a flat screen TV receiver. Additional programmes from external sources can be added as shown, a typical UHF multiplex having a capacity for 32Mbits per second, enough for up to eight HD programmes. This table shows the bandwidths made available in the UK. The terrestrial broadcasters cannot easily add more HD services due to the restricted bandwidths available. Even the satellite operators will be restricted to one programme per transponder when 8K arrives, although they already have more than 50 HD channels. HDMI This is the primary standard for interconnecting video devices in the home. The most common HDMI connector has 17 pins. The three video signals (red, green and blue) are relayed without compression on balanced pairs of wires, thus severely limiting the cable length unless fibre HDMI leads are used. Other wires relay audio, communication, data and control signals, including an “EDID” (Extended Display TV and Data relay in a home environment Robert A Calaz C Eng 43 CAI Feedback Autumn 2018