Southern Oregon's seven-digit telephone numbers soon will join eight-track tapes and manual typewriters on the ash heap of history.

Southern Oregon's seven-digit telephone numbers soon will join eight-track tapes and manual typewriters on the ash heap of history.

The Oregon Public Utility Commission approved Oregon's fourth telephone area code Tuesday. The new 458 area code will be overlaid on top of the existing 541 area code, which means even local calls will have to be dialed with the area code when the change takes effect sometime early in 2010.

The profusion of cell phones, pagers, fax machines and other telecommunication devices has depleted the supply of numbers in the 541 area code. Telecommunications industry officials estimated they would run out of 541 numbers by the first quarter of 2011.

The new plan should give the region adequate telephone numbers for at least 20 years, said Lee Beyer, PUC chairman.

"After weighing the options, we believe this solution is the least-disruptive option," Beyer said in a prepared statement.

Dialing 9-1-1 will remain unchanged and calls that are presently billed as local calls will remain so.

The PUC considered four alternatives to solve the problem, but ultimately chose the overlay because it allows all existing phone numbers to remain unchanged. New numbers will be issued with the 458 area code when the numbers for 541 are exhausted, said Dave Sloan, a telecommunications analyst in the PUC office.

Sloan said business owners complained that they lost clients when Oregon added the 541 area code in 1995.

"People weren't saying good things about the split," Sloan said.

When a third area code was added in 2000, the new 971 area code was overlaid on the 503 area code around Portland.

The overlay had support from Qwest and other major telephone companies. There was some confusion when the overlay started, but people quickly adjusted to 10-digit dialing, Sloan said.

"We had a lot of questions during the first two weeks," he said, "but after you make six or seven calls, it's nothing."

Sloan said there are still many unused four-digit numbers within the three-digit prefixes in the 541 area code, but the supply of three-digit prefixes is nearly exhausted. Each prefix, such as 560 in Prospect, identifies a geographic area for the purpose of calculating toll calls, so you can't just give unused Prospect numbers to, say, Klamath Falls to make more efficient use of existing prefixes.

Each three-digit prefix has 9,999 numbers — the four-digit combinations that follow the prefix. Sloan said areas such as Rogue River (prefix 582) that have relatively few people may have enough unused numbers to continue using 541 for years.

The three digits for the new area code were selected by the North American Numbering Plan Administration, an independent third party that assigns area codes across the United States. Sloan said 458 was chosen from the shrinking supply of unused area codes. The new area code also had to be a three-digit combination that was not already being used as a three-digit prefix, to avoid confusing the automatic switches that route calls.

"The selection process was beyond our control," said Bob Valdez, a spokesman for the PUC.

Sloan said the exact date for the change hasn't been set. During the conversion, telephone users will have a six-month grace period to dial just seven digits before the change becomes final. During that time they'll hear a message reminding them of the impending change to 10-digit dialing.

But the day will come, sometime in the first quarter of 2010, when 10 digits will be the rule, even if you're calling your neighbor across the street.

Reach reporter Bill Kettler at 776-4492 or e-mail bkettler@mailtribune.com.