When connecting a step down transformer what does the h1 symbol denote?

Primary coil

A Step-down transformer is an electrical device which is used to decrease the voltage using magnetic induction. The windings of the primary coil are more than the windings of the secondary coils. h1, h2 notations are used to refer to primary coils. On the other hand, x1, x2 notations are used to refer to the secondary coils of the transformer. In case of step-up transformer, the windings of primary coil are less than the secondary in order to increase the voltage.