In message , at 16:07:13 on Mon, 5 Mar 2012,
Stephen Sprunk remarked:
Returning to trains, at a recent train show, the merchants had radio
based credit card validators. They were wholly self contained and
didn't require WiFi or anything else. A power outlet was nice to
charge the battery but not necessary.

The technology to do this has been available for more than a decade, and
I've seen such terminals at several conventions over the years, though I
can't recall how long ago the first one was.

I've seen technology demonstrations of similar technology at conventions
since the early 90's. But what they often forget to tell you is that
they've parked a mobile base station round back, to provide the
coverage.

There are now even card reader and receipt printer add-ons for
smartphones; I had a taxi driver run my card that way a year or two ago.

There's lots of things you can do if you know you have the radio
coverage. I've even given TV interviews from home, demonstrating "the
future of mobile data". On that occasion the telco had installed a
portable relay station on my garage roof!
--
Roland Perry