What is component 4 in figure T-2?

Component 4 in Figure T-2 is depicted as two separate coiled lines (inductors) placed side-by-side, separated by two solid straight lines. This is the standard schematic symbol for a transformer with a magnetic core. The two distinct coils represent the primary and secondary windings of the transformer, which step voltage up or down through electromagnetic induction. The straight lines running between the coils symbolize an iron or magnetic core, which is highly typical for an AC power supply transformer. This cannot be a single inductor, which would be drawn as only one isolated coil. It is also not a switch or potentiometer, which utilize completely different graphical symbols (breaks in a line or zig-zags).