Years ago I was working for a small company as a technician. We built custom control systems. Our assembly lab and the lunch room were separated by a set of dividers. Often people would come in for a cup of coffee and stop by to see what was going on in the lab.
Our sales manager, Tom (naturally a talkative kind of guy), would stop by and would always critique what we were building.
He would act as though he was the guy buying and operating the system and start pushing buttons as he was talking.
One day I got a hold of a Klaxon horn and knew exactly what to do with it. I wired it to the start/stop latching relay circuit and waited for Tom to stop by.
Sure enough he came in for a cup of coffee, then proceeded to the lab area.
With coffee in hand he started talking and eventually worked his way around to the front of the control box I was working on.
The first thing he hit was the start button and almost ended up wearing that cup of coffee. He was shaking so badly that he had to set down the coffee so he would spill it.
He did however, have enough sense to hit the stop button to turn it off.
We all had a good laugh, but Tom didn’t come around as often after that. And when he did, he didn’t press any buttons.
Good practical joke! Poor Tom, he was just trying to learn the new products in his own way.
Reminds me of a Popular Electronics magazine construction article back in the 1960's called the "Panic Button". If a victim pushed the button the resulting sound made him he wished he hadn't. A version of this was used on a Candid Camera episode.
Also reminds me of a retail store I once worked in. Often this guy would come in, head over to the CB radio display, grab mics, and holler "Breaker, Breaker!"
A new product called a "Foghorn/Loudhailer" became available, had a PTT (push-to-talk) mic, a powerful audio amplifier about 20 watts IIRC, and a trumpet speaker, was intended for use on boats. We set it up on a display shelf, powered, speaker pointing at the customer, and with the mic gain set to max. When that guy spotted it he keyed the mic but did not get a chance to holler "Breaker!". Instead the acoustic feedback through that trumpet speaker blasted him.
After that he left the mics alone.
I remember that Panic Alarm (I was a mere child back then) and may still have the issue somewhere in the basement! As I recall it had a neon lamp relaxation oscillator for the sound and a tube (50C5) as the amplifier, and a standard base red light bulb to attract the innocent. You had to poke a paper clip through a hole in the case to hit the off switch.
Good memory, Stargzer! Would have been about 1964 or 1965. There were 2 neon relaxation oscillators, one was audio frequency and was modulated by the other at about 1 Hz to produce a siren effect.
I was a young teen at the time too, and learned a lot from building this toy.
I can remember a couple more: The "Little Jiffy Fuse Blower" is a small box with a nice label, a heavy duty pushbutton and a wall plug. Pushing the button connects hot to neutral. If you leave it lying around the lights will eventually go out. Also, back in vacuum tube days some guys would leave a charged metal can capacitor on their desk.
Here's one from years ago. One of our system engineers was on business travel and somebody emptied out his sliding desk drawer -- the shallow one where he kept his pencils, calculator, etc. -- and lined it with a sheets of plastic from cut up trash bags. Taped up the plastic nice and tight, then filled the drawer with water to within a millimeter of overflowing...then carefully closed the drawer :)
I am reminded of a circuit by Bob Pease, if I remember correctly, to make a member of staff at National talk in a softer tone. It was an audio noise generator and as the voice grew louder so did the audio disturbance forcing the speaker to raise his voice above the noise in a positive feedback loop. Must've been awfully noisy while "training" the offending party!
I am sure he described this in one of his columns many years ago.
Back in the mid 1970's, I was the Data Operations Manager for a large multi-national trading firm.
Our programmer, the CEO's nephew, was top notch before lunch. During lunch he would consume 6 Rob-Roys. His after-lunch performance consisted of sitting at the console in a stupor that resembled an automaton, occasionally punching buttons or hitting a few keys until 5 pm.
So, one evening, I took my cassette recorder, a Lafayette bench sine/square audio generator and proceeded to make a recording.
The next day, during lunch, I placed the recorder under the console desk and ran the remote control wire to another desk where I sat and waited for my victim's return.
He took off his hat and coat, walked very stifly to the console and sat down. As soon as he pressed the first button, I turned on the recorder... and there erupted a cacaphony of
electronic noises and a mimic'd computer voice yelling: "THAT DOES NOT COMPUTE! ERROR...ERROR...ERROR!" over and over again. Everyone else in the department was in on the
joke, so they all proceeded about their normal routines during this incident.
Looking around and seeing that no-one else appeared to be aware of what he was experiencing, the man got up from his chair, calmly and purposefully walked to the hat-rack, put on his hat and coat and quietly walked out of the office door.
We all were hysterical over the joke and animatedly discussed whether or not we should
tell the man when he returns the next day. But, ...he didn't. Then, after 3 days, we began to
worry... had we gone too far. Nervously, I approached the Personnel Manager and inquired
about the missing man. "Oh, not to worry" was his reply..."He called the other day and
advised us that he is now aware that he has a very serious drinking problem and admitted
himself to a detox clinic for treatment and rehabilitation. His co-worker will be starting
next week to continue the work until he rejoins us."
Nice that so many of you know what life was like in the '60s.
We had an incident in the electronics development lab where I worked when one engineer had persistent problems with the tuning of the filters he had designed, finally traced to supply voltage instability. I had wired all stations along the benches to supply plus and minus 5 and 11 volts dc, stabilised; our design standard for the new fangled transistors that we were using. The supply circuits used a neat overload cutout that reset automatically when the overload was removed but we had never considered the fact that the series regulating transistor became quite hot during the overload and would therefore pass excessive leakage current for a short while after the supply was restored, raising the voltage temporarily out of spec. This was happening because one engineer persisted in using a design that overloaded the supply but he didn't tell us when it had happened. My remedy was to connect a particularly strident alarm bell to operate whenever the cutout was triggered. And THAT had to be manually reset. The sinner protested loudly at this development but was firmly suppressed by the rest of the team. The bell remained but the need for it gradually declined.
At one job it became obvious to me that somebody was doing things on my computer when I was not there. This was a problem because I was writing code to be compiled, and if they opened a code file with the editor in the wrong mode, it would insert control characters, which would cause compile errors. Management assured me that nobody was doing this, and that I was just stupid. My response was to build an alarm system using a large electric bell and a car security alarm siren, and a 30 second delay after triggering. The whole system was plugged into an outlet that was hard to find. The trigger relay was plugged into the plug-strip that powered my computer. One morning a few days later I came in and got a lot of funny looks from quite a few people. But I never had any more problems with people using my computer. I should point out that each of us was assigned our own computer which we were totally accountable for.
In the old days at the cape, a "button pusher" was cured when a dual indicator button was put in his reach. The top half said "Press to Arm". When he pressed it, the bottom lit up with "Release to Destruct" displayed. He was left holding the button down for some time.
I worked for a small electronics controls company. We built our own products and did custom contract work. We needed extra help, so the boss hired a "techno geek" who claimed to be able to do drafting. He was so slow, the system was being built before he had drawings. This job required a control console that was larger than most Craftsman roll about tool carts. We had it set up for testing against a wall. When the boss told him he would have to turn it on and test it because of his delays, we had drilled a hole through the wall and put plastic tubing through the hole and into the control panel. One of the guys was behind the wall with a cigarette. As our "draftsman" pressed the Start button, smoke started billowing out the panel. You should have seen him panic trying to figure out how to turn it off. I don't remember that it got him to speed up any, though.
This is not actually a technical practical joke but it did occur in the technical work place. I call it joking the jokester. One year at Easter time I came to work and found a beautifully decorated Easter egg on my desk. The other people in the office also had eggs. I asked around "who brought in the eggs?". I found out it was the young lady in charge of our spec department, someone who I had played a number of practical jokes on. So after finding out who left the eggs I decided I had better check this out. I took the egg on my desk and tried to spin it on its end. It just flopped over, indicating a raw egg! I double checked a egg on her boyfriend's desk. It spun very nicely on its end, a cooked egg! I then very quietly switched eggs with her boyfriend & clued in others in the office. We had a good laugh when she was trying to explain the raw egg to her boyfriend & helping clean up the mess!
When I was at college, in the library on the wall above the photocopier was a big red button with a sign that said "Do Not Press This Button" -- you would be amazed how many folks did press it just to see what happened (I think it was part of some psychology class/experiment).
When I'm giving a talk to non-engineers, I often tell them that half of the fail-safes we build into our systems are there to tell us when some drongo has turned the other half off :-)
Ok guys, here are my two cents.
What about a button unleashing the obnoxious sound and some sensors to increase the volume as the "victim" walks away XD. He would have to stay closer in order to be safe!
Way back I used to work my way through college in a 2-way radio shop and there were pranks over the years.
My boss would leave charged axial caps on the bench with the leads folded back across the body so that there was a large area to catch both leads with your fingers when he told you to "Clean up that bench!"
I got him back one day when he was probing the plate on the PA of a 100Watt transmitter. I took an empty clipboard and opened the clip all the way and let it go......
He got back for that by putting a christmas tree flasher in line with the power to a console. I spent 20 minutes removing as many screws trying to figure out why the radio audio cut in and out at a 1/4 Hz rate.
So, one day while rumaging through a garage sale I found these HUGE flash bulbs that used a standard light socket.......... You can guess what happened when the boss came into his dark office the following day and reached for the light switch.
In the good old days of DOS based PCAD. I used a editor to change the routine messages on startup of coworkers work stations, "WARNING THIS IS A UNAUTHORIZED COPY OF PCAD AND IS A FELONY IN THE UNITED STATES OF AMERICA. THE PROGRAM WILL BE AUTOMATICLY DELETED."
Somebody was throwing the thermostat next to my bench all the way on or off. SO i out up a sign saying "please don't" to no avail. I was testing battery life on a farm fence charger so I ran the HV loop to a ring around the thermostat and told everybody in the lab. Later that day the president asked me to take it down. I assume got the shock..
I remember one, my boss had a user's manual of a Fuji controller (written in english) and he pass another copy to us (written in japanes) and he started reading the contents aloud. We did not understand a thing...and after surprised faces, he questioned: "can you understand japanese or not?"...later, much more later we discovered the trick...
Classic desktop prank :
I print-screened a colleague's desktop into a bitmap when he was gone for a coffee and made it wallpaper, putting everything on the desktop in a safe place beforehand. We all had fun watching him double-clicking on icons and restarting his pc over and over when nothing seems to work.
Years ago, I was developing an audio signal generator for a well-known T&M company that had a 3-second voice ID feature. I was working late when I got the voice record/playback feature working. Before I left for the day, I recorded a message "Help, Let me out of here!" and rigged it to loop, turned up the volume, and covered my headphones with papers.
I was working late the next day, when the night janitor stopped by to tell me that he was quite perplexed as to who was in distress and how he could help!
CEVA's Eran Briman examines the explosion in vision processing and why it requires a rethink of mobile and embedded processing architectures if the future 'connected vision' paradigm is to be fully realized.