An electric symbol is a pictogram used to represent various electrical and electronic devices (such as generators, motors, batteries, cables, wires and resistors) in a schematic diagram of an electrical or electronic circuit. These symbols can (because of remaining traditions) vary from country to country,but are today to a large extent internationally standardized. Symbols enable professionals around the world to "read" and understand their meaning and use them appropriately.
Symbols in this book are based on IEC 60617 - Graphical Symbols for Diagrams
On this page is a small selection of symbols, including those used in this book, and their meaning. For other symbols the IEC standard should be consulted.
One general rule with the use of symbols is that as long as standard types or combination of those are used no further explanation on drawings is required.
Furthermore any combination of standardized symbols can be made to form a new symbol. The diagrams of a small and a large circuit breaker in chapter 8 on page 57 are examples of combinations of standard symbols.
When non-standard symbols are used, for instance purpose-made, these should be explained on the drawing or on a related document like a list of symbols.

Phase colours 
Phase colours are used to easily identify the different phases, the neutral and the protective earth or ground in an electrical installation.

Unfortunately there is no worldwide standard for phase colours so one should always be cautious when servicing an electrical installation.
Below are some examples of phase colours as they are in use in the US, Canada and Europe.

Diagrams
For the sake of clarity it was decided for the diagrams in this book to use the phase colours as these were officially in use in the UK until April 2006. The phase colours as officially in use throughout Europe as per CENELEC 2006 would have been difficult to read.