People who live in the 740 area code will see a new 220 area code popping up in their neighborhoods beginning in early 2015.
Existing customers with the 740 area code will be allowed to retain their existing numbers under an "overlay" plan approved Dec. 11 by the Public Utilities Commission of Ohio.
PUCO members chose the overlay plan over another proposal that would have split the area in two.
PUCO Chairman Todd A. Snitchler said in a statement the overlay plan was considered "the least disruptive and fair."
Under the overlay plan, once the available phone numbers in the 740 area code are exhausted -- probably by March 21, 2015, according to the federal North American Numbering Program Administration -- the 220 area code will be used for new numbers. Everyone who has the 740 area code at that time will keep it.
During a six-month grace period beginning Sept. 20, 2014, callers will be able to make local calls by dialing either 10 or seven digits. After the six-month period, callers will be required to include the appropriate 740 or 220 area code for all local calls.
The overlay plan was recommended by the Ohio telecommunications industry three months ago.
The plan "operates in a manner that is fair and equitable to all parties," said Dana Crandall, an engineer at Verizon Wireless, in the company's presentation to the PUCO.
Similar overlay plans in Texas and Pennsylvania have shown that the telecommunications industry " can smoothly implement overlays in an effective and efficient manner that minimizes adverse impacts on consumers," said Jon F. Kelly, general attorney for AT&T, in the company's presentation to the PUCO.
In the past, the PUCO had expressed concerns about "the burden and inconvenience to consumers" of dialing a 10-digit number, Kelly said. But the rapid adoption of cellphone use has made such 10-digit dialing part of most consumers' routine calling pattern.
Last month, the PUCO asked for public comment on the plan, and about 70 percent of the more than 900 customer responses were in favor of the overlay option, PUCO spokesman Jason Gilham said.
An increase in "machine-to-machine" communications by gasoline pumps, vending machines and other devices that accept credit-card payments was one of the factors driving the demand for new phone numbers, Gilham said.
"Any time when you're at a gas pump and you're using your credit or debit card, there's a (phone) number assigned to that pump," he said.
The number of gas pumps in Delaware County alone increased 33 percent to 1,252 from 2007 to 2012, Delaware County Auditor George Kaitsa said.