What’s the meaning of this sign?

Restricted parking zones

In some environmentally sensitive areas, where waiting and loading restrictions are uniform, they may be indicated by upright repeater signs, but not yellow lines and kerb marks. These are known as restricted parking zones. The zone entry sign indicates the times when waiting and loading are prohibited. Where parking and loading are permitted, usually in signed bays, this should be indicated on the entry signs. The bays within the zone may be fully marked in the conventional manner or indicated by other means such as a change in surface materials. Upright signs will give details about the use of the bays.