g undertaken in a wide variety of areas associated with radio. Today people require greater 16 Newnes Guide to Radio and Communications Technology degrees of freedom and flexibility, and radio and wireless links are one way in which this can be provided. Fast and flexible communication is also required across vast distances, and again radio provides a cost effective means of providing this. In view of these and other requirements radio is one of the fastest growing areas of technology today. Since their real introduction in the 1980s cellular telecommunications has experienced a phenomenal rate of growth. In view of their cost they were initially only used by businessmen. However, as costs fell their use increased with market penetration reaching levels of 70 per cent in some countries. Now with the new technologies becoming available there is a growing emphasis on using cellular technology for data transmission and remote working. New short-range wireless technologies are becoming far more widely used. Not only are items like wireless controlled door bells, heating thermostats and the like becoming commonplace around the home, but new technologies are enabling items like computer peripherals to talk to one another without the need for many interconnecting wires to be used. This could enable connecting computers together to be far easier than at present. With digital radio now established, this type of technology is likely to grow. Not only does this provide a much greater level of quality than is possible on FM, but it enables many more services to be provided giving far more flexibility to the medium. Apart from introducing new services, many other radio developments are focused on pushing forwards to boundaries of technology. The pressure on the amount of radio spectrum that is available means that higher frequencies need to be used. To meet this need new semiconductor devices are being developed which are capable of operating at fre- quencies much higher in frequency than before. Although these devices may no