OLYMPIA, Wash. (AP) — Required 10-digit dialing arrived in western Washington state on Saturday.

That means residents have to punch in the area code along with the telephone number to make a local call.

The change is needed because a new area code — 564 — is being added throughout the region starting Aug. 28.

The Washington Utilities and Transportation Commission says Saturday was the mandatory start of 10-digit dialing for all western Washington area codes.

New telephone numbers in the 206, 253 and 425 territories will be assigned a 564 area code, initially starting with the 360 area code territory.

State regulators approved the new area code last year.

Officials say alarm, security and medical alert systems should be checked to make sure they are unaffected by 10-digit dialing.