Back in the late 1970's, I was working with a group who were researching electronic telephone exchanges. Our boss 'Ted' (Surname supressed) was a really nice guy who seemed to be the victim of a large number of classic pranks. I joined the group when I was fresh out of college - and most of the pranks (including this one) happened before I started there.
One of these jokes sticks out as particularly memorable: The Mark I Telephone scam .
Whilst we were researching advanced designs for telephone systems, our office had a particularly ancient rotary-dial phone system which was long overdue for replacement. Since the company we worked for also manufactured such systems, when we got a replacement, it was a VERY new design - possibly the first of it's kind. It also had fancy push-button phones - but not the modern tone-signalling kind. These were very unique to the particular telephone exchange we had.
Hence, when the new exchange was installed, the first thing the guys in the telephony research group did was to pull one of the phones apart to see how it worked. (Well, Duh - we're engineers - right?)
They turned one upside-down and unscrewed the lid and immediately discovered that all the keycaps fell off. A little later, they realised that the actual switches underneath were simply separate components clipped into a frame and connected to the circuit board of the phone with some loose wires.
At this moment, the gem of an idea formed. Late that night - and before the new phone system was operational, they dismantled every phone on our floor of the building and swapped the top and bottom row of switches, replacing the keycaps in the normal order so you couldn't tell that anything had changed.
If you pressed the '1' key, it would send a '7' - if you pressed '9', you got a '3' and so on. They called these modified phones "The Mark I Telephone".
Next they wrote and posted a fake memo that appeared to come from the office equipment manager saying that there were some teething troubles with the new telephone system and some phones might not work. Two days later, they followed it up with a second fake memo that said that we had been delivered the older "Mark I Telephone" instead of the "Mark II" that this exchange needs. New phones were on order but in the meantime, it would still be possible to make calls so long as you followed a particular procedure.
Then they wrote up a LONG and horribly complicated algorithm for turning standard phone numbers into numbers that would work with the Mark I phone. Something like: "If the number starts with a one or a three then add 600 to the number unless the second digit is also a one or a three in which case add 660 to the number. If the last digit is odd then add 6 to the number unless it is a 7." ... basically, a long set of instructions that had the effect of swapping 1 for 7, 2 for 8 and 3 for 9. We only had three digit extension numbers - so that wasn't too bad.
Well, everyone in our group was 'in' on the joke except Ted - our boss. He wasn't too suprised that the new phone system had teething troubles - but the complexity of the algorithm did seem a bit much. To his credit, he did manage (with some difficulty) to dial numbers by working through the steps outlined in the memo.
What suprised him was how his engineers could look at a phone number - gaze into space mumble meaningless numbers and count on their fingers for a few seconds - then immediately dial it correctly! They seemed to have memorized the algorithm with little difficulty and had developed the ability to calculate the number change in their heads! Ted knew the guys were good at math - but you could tell that he was just a little intimidated at the difference between their mental agility and his!
(In reality of course everyone just knew to mentally swap the top and bottom rows of the keypad - which is easy!)
After a week or so of this, Ted had eventually written down a 'crib sheet' containing all the numbers he called frequently in the "new" format and the joke was getting stale. Hence, the engineers did a midnight raid and rearranged the phone buttons once again - this time swapping the left and right columns of numbers. A new 'fake' memo was issued saying that the telephone exchange had been fitted with a "Mark I Telephone Conversion Kit" to fix our earlier problems but that it appeared that our phones were actually "Mark I(b)" phones and not the original Mark I(a)'s as we had originally suspected. A new (and equally complex) algorithm was appended to the memo to allow users of Mk I(b) phones to operate on the older Mk I(a) signalling system.
Well, at this point, Ted went ballistic and phoned (with great difficulty) the office manager to complain. Needless to say, the poor guy had no idea what Ted was ranting about and denied sending any memo's - so the joke was soon over.
I believe this is a true description of the events - if anyone knows better, I'd be happy to accept corrections. If Ted is listening...we're Sorry!