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The problems which existed in the early days have been completely eliminated and the lower burden and greater accuracy of these types of relay means that they are now the usual type of relay to be selected.
This does not mean that electromechanical relays have disappeared. Far from it. They still feature in the vast majority of installed equipment and so are still discussed at length in this new edition.
It would not do for me to ignore the help I have been given in preparing this new edition.