The new 442 area code overlay, now optional, becomes mandatory throughout the 760 area code region on Oct. 24.

Starting that day, all calls made in North County must include the full number, including area code. Even if you're dialing across town or across the street, the familiar seven-digit number won't be enough anymore.

Here are the basics: Those who already have 760 area code numbers will keep them. But new numbers in the area will get the 442 area code. Because two area codes will cover the same area, specifying the area code will become necessary to make all calls.

And because such a change takes some getting used to, dialing under the new system became optional on May 2. If you haven't already begun preparing for the overlay, you've still got several weeks to get ready.

Here are some tips from regulators and phone companies to ease the transition:

-- Dial the full number, including area code.

By switching to dialing the full number now (including 1 for land lines), when the change is still optional, you'll avoid any unpleasant surprises when Oct. 24 rolls around.

-- Check all equipment and services that use the telephone system.

Burglary alarms and gated community entrance parking sometimes work on dial-up networks, as do faxes and modems. Speed-dial numbers on cell phones and land lines will also need to be changed to the full number.

-- Tell personal and professional contacts of the change.

It's convenient to make a list of who to tell while reprogramming your speed-dial numbers. Also, look over your recent phone bills to identify who needs to be contacted. Update contact numbers for schools, doctors and banks.

-- Add your full number to newly printed business cards and stationery.

Give them out early, so your customers know well in advance how to contact you.

The change was ordered last Oct. 16 by the California Public Utilities Commission, because new numbers in the 760 area code were beginning to run low, largely because of North County's growing urbanized population.

The overlay decision reversed an earlier order to split the 760 area code and assign North County to 442. Strong protests from North County residents caused the PUC to change its mind.

Once the overlay becomes mandatory on Oct. 24, those who don't dial the 10-digit number will get a recorded message to dial the complete number. Automated services that require a correct number will just stop working.

Still have questions?

The Keep760.org Web site provides information on the area code overlay.

And www.calphoneinfo.com, which is operated by the utilities commission, has information on the overlay and much more. The commission's phone number is 800-649-7570.

Contact staff writer Bradley J. Fikes at 760-739-6641 or bfikes@nctimes.com. Read his blogs at bizblogs.nctimes.com