Starting Saturday, people with the 510 area code will have to work a little harder to get their calls through.
That's because on that day, in preparation for a new area code, people will have to dial 1 plus the area code plus the phone number of whomever they're trying to reach, according to the California Public Utilities Commission.
A month later -- on July 22 -- the Bay Area will welcome a new set of numbers to its growing area code collection.
The new 341 code will co-mingle with the 510 area code in the western parts of Alameda and Contra Costa counties, CPUC officials said.
This won't require people to change their phone numbers or area codes but it does mean that people with either the old area code or the new one will now have to follow the new dialing procedure.
If callers don't use the new procedure, they'll be regaled with a recorded message instructing them to hang up and try it again.
People can still dial 911 and other three-digit numbers, like 311 and 411, without first dialing 1.
All automatic dialing equipment -- including fax machines, alarm and security systems, medical monitoring devices, call forwarding and voicemail services, among others -- will need to be reprogrammed, the CPUC said.
People getting new telephone numbers will be assigned to either the 510 or the 341 depending on availability.
The decision to add the new area code came as 510 moves closer to exhaustion, with nearly 8 million numbers already assigned to that area code.
The 510 area code was created when it was split from the 415 code in 1991. It was split again in 1998 when the 925 area code was created.
The 510 area code serves the cities of Alameda, Albany, Berkeley, Emeryville, Fremont, Hayward, Newark, Oakland, Piedmont, San Leandro and Union City in Alameda County; and the cities of El Cerrito, Hercules, Pinole, Richmond, and San Pablo in Contra Costa County.