Before the widespread adoption of this standard, different countries and even different companies within the same country used conflicting conventions. For example, the direction of positive current flow (conventional current vs. electron flow) or the sign convention for mutual inductance could vary, leading to errors when international teams collaborated on a single project.
National versions, such as from the British Standards Institution (BSI) , which is technically identical to the IEC version.
The standard defines how to assign reference directions for current and reference polarities for voltage. It clarifies the difference between: