What happens if we run out of phone numbers?

(WYTV) -- If you watch old TV shows, you may recall silly-sounding phone numbers -- like MU5–9975 -- used to patch through to your favorite sitcom stars. That old system -- using two letters and five numbers -- became outdated and was replaced. Could we get to that point with our current seven-digit numbers?

We started switching to the area code system we have today in 1951 when New Jersey was given the 201 code, the country's first. Early on, the country used 86 area codes. But the U.S. population has more than doubled since the 1950s, and now, we have 335 area codes.

Will we run out at some point? Experts say we aren't all that close yet, but it is possible, and we have some options.

Several number combinations are not possible. For instance, your area code can't be 911, so the total number of possible phone numbers is a little more than 5 billion, and more than half of those have been given out, according to How Stuff Works.

While that leaves us with a massive number of currently unassigned numbers, many individual area codes rely on recycled numbers or have run out of available combinations entirely. When that happens, new area codes are added, often as an overlay, meaning the second area code covers the same geographic region of the country as the original.

If we were to use all available area codes, we would need a new system.

An organization called the Alliance For Telecommunications suggests adding one digit to the area code and one to the dialing prefix. That would add 640 billion more possible numbers and expand the system well past our lifetimes.

But others say that by the time we start running out of the standard 10 numbers we have today, we will have found new ways to talk using internet technology and we won't need traditional numbers.

That would make 10-digit numbers obsolete, which could mean generations of future TV watchers confused and amused by our years of 10-digit dialing.