Evolution of television receivers from analog to digital

Digital circuits were introduced into TV receivers for control purposes, for example, remote control, and later for internal integrated circuit (IC) control via a data bus within the receiver. Recently, an external bus system was proposed that allows digital control of a variety of in-home consumer equipment. There are two reasons for extending the digitization of the receiver to the video signal processing in the receiver. Firstly, digitizing existing functions will reduce the cost and increase the reliability, and secondly, new functions will enable extra features and better picture quality to be obtained. The key components are complex, fast VLSI ICs and especially for the new features: the integrated digital field store. Examples of both approaches are given and the choice of sampling frequency, important for both approaches, is discussed. Teletext is a service already popular in many countries. Its viability is due to the early availability of complex digital ICs at economic prices. A review is given of the operation of teletext in the TV receiver and a description of the various system standards is attempted. The future use of time-multiplexed color-TV transmission systems, such as the C-MAC and D2-MAC/Packet systems (MAC = Multiplexed Analog Components), is considered. Decoders for these systems will probably use digital methods. Moreover, when digital field storage and processing are introduced in the TV receiver, interesting extensions to the MAC approach will become possible.