Why In Figure T-2, component 4 is drawn as two coil windings facing each other with parallel lines between them representing an iron core. That is the standard schematic symbol for a transformer, which couples AC energy from a primary winding to a secondary winding by magnetic induction and changes voltage according to the turns ratio.
Watch out A variable inductor would be a single coil with an arrow drawn through or across it; the tell for a transformer is the second winding plus the core lines between the two coils.
Two coils face to face with core lines between = transformer. One coil alone = inductor.