Nice look back at life prior to the onslaught of computers and devices. Going into that MIT lab and seeing the spread of computers must have been eye-opening then. Today, you'd see a comparable set up in an office and even in some homes. Also pretty eye-opening that the FCC wasn't governing the computer spectrum back in those days. Shows you that Bill Gates' vision (and others) of a computer on every desk was still pretty much considered a pipe dream.
Frank, that was an iteresting experience. Today we have a similar issue with cell phones. I am not talking about the regulatory situation, but about interference with audio equipment. My son first told me about it in regard to a situation in middle school. Students were not to have cell phones in school. If they had them, they were to be turned off. Often, though, they were not. In classes with computers the teachers noticed a buzzing sound coming from the computer speakers. They soon figured out that it was the cell phones, and it allowed them to "catch" those students who had their phones with them. Now this happens only with the at&t GSM phones. I had a Verizon phone which used a different frequency and transmission type (CDMA). I did not notice interference with audio equipment with those phones.
I have the same problem in my car. When my ATT phone talks to the tower to change towers, it transmits and meses with my radio. I have to have it far away from the receiver to avoid the irritating buzzing. But I don't blame the cell phone. After all, who expects to place a transmitter so close to a receiver without interference? That's why we squelch the radio during transmit, normally, in ham radios. Plus, we aren't always duplex, but that is another story.
Back in the mid '60's I remember hearing Christmas carols "played" by an IBM 1620 computer via an AM radio. Someone said a program caused certain sequences of clock signals that radiated the "music" the radio picked up.
Tonight I found this: "From Bill Principe, 16 Sep 2005:
I saw your 1401 and 1620 pages on the Internet. As an undergrad at Berkeley in the 60s, I had part-time jobs working on both machines. I'd like to share a 1620 anecdote.
There used to be a program for the 1620 that worked line this. You put an AM radio on the CPU console, and tuned it for the loudest noise. (They generated a lot of random RF noise that could play havoc on nearby electronic equipment.) Then you fed a deck of cards with the program. The radio would play "Stars and Stripes Forever" and the line printer would play the drum rolls. I'd like to see a Pentium IV laptop do that!"
Here's the source: http://www.columbia.edu/cu/computinghistory/1620.html, so it seems as though programmers pretty well mastered creative uses of computer generated RFI some time ago.
Back in the early days of computing we did some pretty crazy stuff to make music. Most small computers had cassette ports for saving programs and that was hacked into for music. There was another one for uploading code into a Commodore floppy's RAM so that the stepper mode could sing, but my favorite was using a dot matrix printer.
No knowledge is wasted, I still use the singing motor and sometimes solenoids in appliances as a beeper.
Yes, audio interference from AT&T GSM phones is very common if the phones are close to a speaker. My wife's old RAZR flip phone does it ,as does my co-worker's iPhone 4. As the other poster mentioned, it seems to happen when the phone is searching for towers. My wife's phone will also generate the noise just before her phone rings. Quite annoying.
Since I switched to a Sprint phone, I haven't heard the sound once, so it seems to have something to do with the frequency that the AT&T GSM phones operate on.
The GSM poll rate is 277 Hz, right in the audio spectrum. I live in a low-signal area, so my GSM cellphone is always transmittting near maximum power. It's tone can be heard on the laptop speakers and on my wireline phone if I don't place it carefully, and I am sure I could hear it on AM radio if I tried.
The previous few generations of ATM (cash) machines generated a fanfare at the conclusion of a transaction by cycling the receipt printer printhead back and forth at the appropriate rates and distances.
Years ago, my wife would call out to me that the TV was messing up. Living in a rural community, but during the height of CB popularity, we assumed it was a neighbor using their CB radio, possibly with an (illegal) power amplifier. This went on for weeks and we coined the phrase DCB for "Damn CBers". One night it hit me though - the only time she complained was when I turned on my new Osborne computer. Apparently there were enough harmonics coming from the blazing fast 4 mHz Z80 processor chip to interfere with the television rooms away. That solved the mystery of who the DCB was, it was me. In those days, I only occasionaly used the computer unlike today when it is hardly ever turned off and since I was constantly fiddling with something in my basement workshop, it took some time to make that connection.
Siemens and Georgia Institute of Technology are partnering to address limitations in the current additive manufacturing design-to-production chain in an applied research project as part of the federally backed America Makes program.
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Independent science safety company Underwriters Laboratories is providing new guidance for manufacturers about how to follow the latest IEC standards for implementing safety features in programmable logic controllers.
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