Schematic symbols in the transformers category.
An autotransformer uses a single winding with a tap to provide variable voltage output. The symbol shows one coil with a sliding contact or tap point. Autotransformers are more efficient than standard transformers for small voltage adjustments.
A transformer transfers electrical energy between circuits through electromagnetic induction. The symbol shows two coils (inductors) side by side separated by parallel lines representing the iron core. Transformers step voltage up or down for power distribution.