A draftsman knows what symbol is used for a GFI.
An electrician knows how to install a GFI.
An engineer knows that an op-amp is used in a voltage amplifier arrangement to remove clamping current from the miniature contactor when the toroid sensing coil detects a net magnetic field due to unbalanced current flow to make a GFI work. But proably couldn't pick out a picture of one in a lineup.
