In the works since December 2014, Suffolk County’s second area code — 934 — is finally set to see the light of day on Saturday.

That means that anyone in Suffolk seeking new residential, business or wireless service, an additional line or possibly a move of their service, may be assigned a number with the new code. (Existing 631 phone numbers remain the same.)

Getting a 934 number, though, will not be a slam dunk as of Saturday.

Some carriers may still have a ready supply of 631 numbers, so the introduction of the new code could take time to build up steam, said John Manning, senior director of the North American Numbering Plan Administration, which oversees telephone resources, including area codes.

Preparing for this two-code approach, callers in Suffolk have already made the leap from the familiar seven-digit dialing without an area code, to 10-digit dialing for intracounty calls.

Despite a nearly yearlong grace period for optional 10-digit dialing, some callers were stymied on June 18, the first day the area code was required.

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Some questioned why those with 631 numbers had to join in the 10-digit dialing party. Couldn’t they stick with seven, and have the new 934 people take on the chore of having to tack on the code — be it 631 or 934?

Not a go, said Manning.

That would mean some service carriers — those with a supply of 631 numbers — could have an unfair advantage over new carriers that would have access only to numbers with the new code. Also, such a dual-dialing approach “creates significant complexity” in how the network would have to process calls, he said.

This is all coming about because 631, which was created for Suffolk in 1999 after it split from the Island’s 516 area code, “is running out of assignable telephone numbers, and implementation of a new area code is necessary,” said a June 16, 2014, report from the state Department of Public Service.

It was decided in December 2014 to take an overlay approach in which current Suffolk customers would keep their 631 numbers, with new customers assigned the new code “as needed.” The other option envisioned a “geographic split,” with Suffolk County residents on one side of a line keeping 631 and those on the other side making the switch.

Each new area code starts out with 800 prefixes — the three numbers after the code — with a few prefixes, such as 911, not assignable, Manning said. At this point, the 631 code is down to about 30 prefixes, he said.