“About a dozen different types of component are used in the circuits contained in this book and in other transistor circuits. Each type of component has its own symbol and the meaning of these svmbols must be understood before a circuit diagram can be properly interpreted. Circuit diagrams are merely intended to show what components are used in a piece of electronic equipment and the way in which they are connected. They do not show what physical position each component has in the equipment. It would be possible to use drawings of the individual components in such a diagram and this is sometimes done but it becomes far too clumsy a method where complex circuits are concerned, Some of the earlier circuits in this book have both circuit diagrams (those usrng symbols) and wiring diagrams (those using actual illustrations of the components). These should enable the constructor to gain a knowledge of the circuit as a whole. One important point to remember is that specification of a component does not necessarily indicate the size or shape of that component. For example, if a 500 pF tuning capacitor is specified and no other details are given any 500 pF tuning capacitor may be used. The size and shape of 500 pF tuning capacitors made by difierent manufacturers vary enormously, as do the prices and in this case the choice is up to the con^tructor. If, however, a particular make of 500 pF tuning capacitor is specified, this make should, if possible, be used since its size has probably been chosen by the designer to fit in well with the set. It is not always necessary to adhere precisely to rue specification given for a component but it is difficult for a beginner to know when deviation is possible and to what degree. In this chapter some indication of generally permissible deviation is given and thr6ughouf thle Uoot the possibilities for deviation in a given circuit are outlined. The constructor should take note of these indications since they will help to provide the experience he needs”