Such engineering nightmares are reminiscent of "The Sorcerer's Apprentice"! When I was a considerably larger child --- pushing 30 years old, no less --- staying late alone at the office as usual but temporarily unable to make progress on a project, I absent-mindedly picked up the telephone. Our lab had been grafted onto a previous establishment: in particular, to call an extension there it was necessary to prefix an 'area' code, and vice-versa for them to call us. So I dialled their code; then having no-one to converse with, I dialled ours; then still having no-one else, I dialled my own extension, which was of course engaged; and I replaced it. It next occurred to me to wonder how much redundancy was available across the link, so I began dialling their code, ours, theirs, etc. At the 7-th return I received a busy tone, which answered that question. Then discretion appears to have deserted me. I dialled to-and-fro 6 times, followed by my own extension. Which was of course again engaged, and I replaced the receiver while resolving to stop wasting time. It immediately began to ring. I picked it up, and heard an engaged tone. I replaced, and it rang again. Uh-huh ... Eventually, I had to fix a bent paperclip in the dial to keep the damn' thing quiet, and slunk off home. Next day I was coolly informed that the technician responsible had been obliged to resort physically to prising open a relay inside a cabinet in order to unblock the system. Fred Lunnon On 6/10/18, Keith F. Lynch <kfl@keithlynch.net> wrote:

"David Wilson" <davidwwilson@comcast.net> wrote:

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Tomas Rokicki wrote:

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I suspect the laws of mathematics may have changed over those 34 years.

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Or at least the fines and jail terms.

I once got in serious trouble for breaking the law against dividing by zero.

When I was a small child, my father let me visit his office and play with his electro-mechanical calculator. He warned me not to divide by zero, but I did it anyway. The machine started grinding away, and kept going and going. Pulling the plug made it stop, but it started again as soon as it was plugged in again. He told me it had to be sent back to the factory for repairs.

For youngsters who have no idea what I'm talking about, I found a video of someone doing the same, only on a machine that has an interrupt switch: https://www.youtube.com/watch?v=7Kd3R_RlXgc

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