Elevating cost-cutting to a whole new level with million-dollar bar bills

The curse of RS-232 strikes again in part two of our serial series

On Call While the days may seem to be blurring a little at the moment, we can assure you that it is Friday, which means it is time for another in The Register's series of reader experiences at the hands of the On Call telephone.

Readers might remember Jeff from last week, and his A-Team-esque paperclip solution for an RS-232 diagnosis. Today's instalment sees him back in action, dealing with charges on a bill that would make even the most avaricious stuffer of the hotel mini-bar say, "Steady on, old chap."

The call came in complaining that hotel guests were seeing multiple million-dollar charges appearing on their bills. This was, of course, back in the 1980s when a million was a lot of money.

Heck, it is still a lot of money unless, of course, you're trying to fit wheels to an Apple computer.

The customers, recalled Jeff, "ate in the restaurant and when the restaurant management system sent the charge, the charge that was received was wrong by millions of dollars."

It was then followed by the correct charge.

As with last week's telephone shenanigans, the restaurant system was on one end of the hotel while the computer was on the other, as well as being on an entirely different floor.

This time the paperclip trick wasn't going to cut it and so Jeff, along with the vendor of the restaurant system, flew out to the hotel to look into the problem.

"The interface," he recalled, "was a simple 'send and pray' format of 'data<cr>' just like a printer or teletype machine would use."

Those were indeed simpler days, before every IoT edge device needed to be a fully fledged server running Kubernetes in order to itemise a customer's bill and point the finger of guilt at who ordered the wine and which greedy so-and-so had three starters.

"We ran wire down the halls and through stairways, so we could tap the data connection and sit at one location and watch what was happening," he told us.

The pair watched and saw many requests get corrupted (hence the million) but the system self corrected. It was a mystery – a short in the wire somewhere? Something in the software? Computers weren't cheap in those days, and a hardware fault would be less than ideal.

As the duo scratched their heads, the elevator could be heard down the hallway. As it passed, a corruption event happened. Another elevator passed. Another corruption.

"It dawned on us that the RS-232 connection was run through the elevator shaft..."

The power used by the elevator was being picked up by the cable, which was acting as an antenna and causing corruption on the line. So if someone called an elevator while figures were being transmitted, the glitch would occur.

"The fix," he laughed, "was $600 line drivers."

Jeff had another story to tell, about the time he got a call reporting "a computer crash," which turned out to be the result of a car hitting a kerb and smashing through the wall of a hotel's computer room, but that will have to wait for another day.

Ever been called out to the scene of a computer foul-up that involved four wheels and some careless driving? Or seen interference on the line do the most unexpected things? You have? Send an email to On Call and tell us all about it. ®