power indicator  definition
However, to say that power is the ability to produce intended and foreseen effects, and that no one form of power is more basic than any other, does not mean it is a simple matter to study the power of a group or social class. It is necessary to develop what are called indicators of power.
The power symbol was the result of the logical evolution of a simple user interface, with most early power controls being simple switches that were toggled between two states demarcated by the words On and Off.