ity Figure 2.1 Fleming's diode valve. Reproduced by permission of the Science Museum/Science and Society Picture Library SSPL 10 311 209 Figure 2.2 Lee de Forest's triode valve. Reproduced by permission of the Science Museum/SSPL 10 324 050. Making Telecoms Work PHILIPS Figure 2.3 The EF 50 valve - an example of the evolution of component technology over time. Photo Jacob Roschy, Radio Museum.6 This provided the basis for the beginning of medium-wave and short-wave radio broadcast- ing, for example in the UK the formation of the BBC in 1922 and fourteen years later the first VHF television broadcasts from Alexandra Palace in London. Television created a demand for television receivers that in turn created a demand for valves and tuned circuits capable of working at VHF with sufficient dynamic range/gain control and receive sensitivity. In the late 1930s, NV Philips of Holland had designed a new high-gain, low-capacitance series of all-glass valves, the EF50 series shown in Figure 2.3. These were used to produce televisions that would work more effectively in areas with weak reception. This valve was also used in radar products and two-way radio systems. As such it has been described as 'the valve that won the war', which is debatable but at least illustrates how the application of engineering development effort allows an enabling technology to improve over time. As valves became smaller and more efficient both in terms of audio amplification and RF (radio frequency) amplification they could also be packed more closely together but this required a parallel development in interconnection technology, the printed circuit board. An example is illustrated in Figure 2.4. The vacuum tube therefore enabled a mass market to develop in broadcast receivers, transformed military and civilian mobile communications and transformed the economics of telephone networks. Valves still live on today in high-end audio and guitar amplifiers and can be sourced either as original components or replaced with newly built modern equivalents