Suffolk County's new area code is 934, the state Public Service Commission said Friday.
The announcement comes a day and a week after the commission approved the county's second area code, to be activated before the third quarter of 2016.
To provide area code relief as required by federal law, the commission examined "overlay" and "geographic split" options. Based on its review, the commission decided that an overlay method will be used in assigning the new area code.
This option is easier to implement from a technical standpoint and less expensive from a customer standpoint, especially for businesses, according to the commission.
Under an overlay plan, existing telephone numbers remain unchanged, and all new telephone numbers will be assigned the new 934 area code.
With an overlay, even calls to a number in the same area code would not be completed without first dialing the three-digit area code, and then the seven-digit number.
The move comes after a public comment period of about four months.
"Years ago, most families would have a single telephone number," commission chairwoman Audrey Zibelman said in a statement last week explaining the need for the new code.
"Today, each household and place of business may use several phone numbers, in addition to the numbers assigned to their landlines and cell service," the statement said. "Given the reality of the way we communicate today, a new area code is needed to expand the numbers that are available."
At the root of it, 631 "is running out of assignable telephone numbers, and implementation of a new area code is necessary," said a June 16 report from the state Department of Public Service, which suggested two options for discussion.
Suffolk's new code will bring to 16 the number of area codes in the state, up from the original five.
With Gary Dymski