This figure demonstrates a common operational error perceiving the unit state, in case of indication fault.

If the unit operation is equipped with a single power indication, the operator might not be aware that it is burnt, and might believe wrongly that the unit is idle, and consequently might handle it carelessly.

To make sure that the operator is aware of faults, the unit might better be equipped with two indicators, on that it is On and one that it is Off, as demonstrated here ...

Updated on 13 Dec 2016.