In the late 1970s, I was doing my training at the Posts and Telecommunications Engineering College in Rhodesia (it is now Zimbabwe, which shows you how long ago this was and how old I am…).
As part of our training we were required to strip and rebuild a Creed 7B Teleprinter, a mechanical marvel which was a sod to work on – adjustments were done with tensions and clearances and screws and locknuts.
The college had a room full of these beasts, which had been taken apart and reassembled by generations of engineering trainees. In the corner was a patch panel with connections to each sender and receiver – usually your own sender was patched to your own receiver and so (if you had everything right) what you typed on your keyboard came out on your printer.
One of our class was a young Irishman who I seem to remember was called Joe, but being Irish everyone called him Paddy. A friend and I had our machines working while most of the class were still completing their adjustments. So we thought we’d have some fun with Paddy. We patched my transmitter to his receiver and vice versa, and waited for him to start testing.
Eventually he had his machine together and began typing….RYRYRY which in the 5-bit teleprinter Baudot code is alternated 01010 and 10101 characters and thus probably the best codes to test with.
So I typed SASASA back to him. He did not pick up the slight delay in my return and looked puzzled and started checking his machine again. In the other corner my friend and I could barely contain ourselves.
After checking his teleprinter again he typed some more. And every time he did we would type something different. And sometimes type the odd character out of the blue. How he did not see us sniggering to ourselves I will never know. We were nearly wetting ourselves.
Eventually we took pity on him. The next time he typed, we typed back “You’ve been had, you daft Irishman!!!”
His response to us was not kind, but was tempered with the happy knowledge that his machine was in perfect adjustment.
And he got his revenge. The place in which we were staying provided us with sandwiches for lunch every day, however at least two thirds of them were made with lots of margarine and slices of a particularly vile kind of polony which we loathed, and hence threw them away. The next day he surreptitiously retrieved them from the bin and wiped them all over my car windscreen.