The diagram (figure 1.1) shown on the previous page is a fairly sketchy one. It gives us an idea of the overall structure of the system, but it doesn't tell us anything about what's going on inside any of the boxes. The diagram is a schematic one. It has more in common with the drawings in Viz than with a photo! It doesn't really tell us how any of the things shown actually work. If we just want to buy a Hi-Fi & listen to it this may not matter. In the end, the main thing is that it should sound good, no matter what's inside the boxes. However, you're more likely to choose the 'best' Hi-Fi if you take an interest in what's inside the boxes. And if you want to understand, modify, design, or build Hi-Fi you need to take a keen interest in what's going on inside!
Most of the diagrams electronics engineers use look like the examples shown in figure 1.2. Just like figure 1.1, these are stylised, but as individual components. The level of stylisation and the symbols used depend upon what's required. The symbols for things like transistors, capacitors, etc, aren't meant to look like the actual components. Similarly, their arrangement in the diagram shows their functional relationship. It's usually not a reliable 'map' showing where they are placed on the actual circuit board. This abstract quality can be confusing at first but it gives us the freedom to choose different manufacturer's components and lay them out on a circuit board as we like. This flexibility can be useful when building a circuit from a diagram.
It doesn't matter if you don't understand the diagrams shown in figure 1.2, they are included purely for illustration. Don't panic, this is the written language of electronics. There is no real reason to expect the meaning to be 'obvious' until it has been explained. You have to learn the rules of the language before you can use it - just as you would if you were sent to foreign country. At this point all you have to do is realise that circuit diagrams are a written language that can be very useful once you've learnt it. The good news is that for this course you won't have to know very much about this language.
Content and pages maintained by: Jim Lesurf (firstname.lastname@example.org)
using HTMLEdit2 on a StrongARM powered RISCOS machine.
University of St. Andrews, St Andrews, Fife KY16 9SS, Scotland.