We may joke that nobody uses pay phones anymore, but that isn't quite correct.

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They stand on street corners and in airports like miniature museum exhibits of another era. Who needs a pay phone anymore? We have our smartphones; they do so much more and they fit in our pockets.

But that doesn't mean pay phones have run their course in the world. For people who are down on their luck, public pay phones are the phones they've got -- and without any pocket change, you can still call the toll-free lines of social-service agencies, which, operators say, is where many pay-phone calls go, according to a report in USA Today by Janine Zeitlin.

Thomas Keane, the CEO of Pacific Telemanagement Services, the largest public pay-phone company in the country, says that is only takes about two or three calls a day for a phone to make a profit, and the company's revenues are near $100 million. They operate some 45,000 public pay phones. "We're sort of the last guy standing on pay phones," Keane told USA Today. "I call it my buggy-whip strategy. I'm sure somebody somewhere is happily making buggy whips at some level."

Some of the demand for pay phones comes at airports where, presumably, international travelers don't have Amercan cell phones. But much comes from places serving a less fortunate demographic: correctional facilities, transitional housing, substance-abuse-recovery centers, homeless shelters, jails, and prisons. Zeitlin reports:

Still, industry leaders believe there is a future for pay phones.

"There's an enormous growth of people below the federal poverty line," Keane said. "This is not anything that makes me sleep better at night, but our business is people who have literally scraped two coins together."

But that sort of bullish thinking may be wishful. Zeitlin finds that "industry leaders say the prognosis is grim without support from the government to level the field with free cellphone providers and to enforce rules that require long-distance carriers to pay operators." One tells her, "It hasn't hit the bottom yet, although it's close."

Anachronistic technologies can be little hints of larger societal patterns. When we see a weird technological holdout -- the prevalence of fax machines in Japan or the persistence of graphing calculators from 1999 -- we can use the example to see particular economic, institutional, and cultural factors that enable, or even require, the technology to persist.

The persistence of the pay phone is a reminder that a growing number of people are being left behind, unable to afford the communication technologies that have become almost a necessity. And what happens if the phones totally disappear, as some fear? Its users will be, like the handset in an out-of-order phone booth, left hanging.