There ain't no problem that can't be solved with the help of American horsepower – even yanking on a coax cable

Playing tug o' war with a 1970s IBM mainframe

On Call Is it October? Already? It feels like we still haven't moved on from March. Put such discomfiture to one side in favour of a Friday treat – a tale of brute force and ignorance from those that are forever On Call.

Today's story takes us back to the mid-1970s, "the Triassic age of computers," as our reader "Chuck" put it.

"The mainframe ruled," he recalled, "and the Rex of the... species was IBM. The punch card was still prevalent but beginning to evolve into input by 8" floppy and the growing number of data-entry terminals."

Those with long memories might remember the IBM 3270 series of terminals, the descendants of which could be found frustrating users until the latter days of the last century. Chuck remembered the 3278 being the most prolific of the breed: "This was a text-only 'green screen' that displayed 80 x 24 characters with a reserved line at the very bottom to give a few status indications."

The thing was about the size and weight of an old 17" CRT and popped up in industries around the globe. Thirty-two could be connected to a controller ("usually a 3271 or 3272," said Chuck) which was then connected via a high-speed (ish – this was the 1970s) channel to a mainframe. The terminals themselves were connected via ordinary coax, which allowed the kit to be quite some distance away from the controller ("a thousand feet," reckoned Chuck).


Help! My printer won't print no matter how much I shout at it!


Chuck was working in IBM's service branch back in those days and had been well trained in the 3270 system. He had been placed on a three-month stint in a call centre supporting field technicians.

"For younger readers to whom the term 'Call Centre' or 'Help Desk' gives memory of rage-induced breakage of handset or keyboard, in those days they were staffed by people who were trained on the product or software, who spoke your native language, desired to help, and would stay on the line as long as needed, even into the night if the problem was severe. Really," he reminisced.

The call came in from an on-site operative faced with an unusual problem. A new terminal had been set up in a bank that would not "see" its controller, which was some distance away.

"The coax metered OK," said Chuck, but swapping out the terminal with a known good one made no difference, nor did replacing the circuit card in the controller. Perhaps the distance was causing a timing issue, but after the software team took a look, it was decided that it had to be the cable.

Another cable was pulled through and had the same problem, "with the contractor pointing the 'I told you so' finger at the service person."

Troubleshooting continued for the rest of the day, but still success eluded the team.

It was no good. A team from the factory would have to be dispatched, and the expensive trip was about to be made when the field operative ("Customer Engineer" or CE in IBM-speak) called again. The problem had been solved.

In desperation, the CE had walked the 500 feet of underground cable in the hope of finding some giant electromagnetic emitter that could be screwing with the signals in the coax below. He reached the end, "then noticed that the spool of wire that had been ordered to length still had a hundred feet left on it..."


A few pointed questions and (we imagine) a shuffling of feet later, and the solution to the problem was found. The cable had been pulled through by what Chuck called a "gang of heavies". A tough job, and the team had eventually hit on the brilliant wheeze...

... of simply tying the pull rope for the coax to a handy pickup truck and letting Ford's finest take the strain.


"Of course," said Chuck, "the cable was now stretched to only half of its original diameter and the electrical characteristics were obviously far beyond anything that the equipment could recognize.

"The service call was terminated, and the problem never heard from again."

Ever had to deal with a "solution" that involved a pick-up truck and a leaden foot? Or done an empathetic 500 feet walk in someone else's shoes during support call? Share all with an email to On Call. ®

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