Electricity changing frequency during wartime?

Years ago, I was on the mailing list of several military surplus stores and always looked forward to getting the catalogs of all of the weird stuff that the military didn’t need anymore. The focus of these stores was radio and electronics, not uniforms and MREs. Next to the pieces of WW2 bombsites and backpack radios, one of the companies sold a small device that looked to be the size of a current weather radio. As I recall, it was really simple. You plugged it in and there was a green light, a red light and an area with holes for an alarm to sound.

This was probably in the late 70s or early 80s so my memory may be failing me. But my recollection was that this device would display the green light when it detected electricity running at 60hz, and display the red light and sound the alarm if it detected 50hz. The implication was that if WW3 started, the power companies would change to 50hz for some unexplained reason, and that this device was an early warning device, surplus from military housing. Since this was military surplus, the device could have been from any era between the invention of electricity and the late 70s.

Was there ever a plan or good reason to change the grid from 60hz to 50hz in time of war? Or was this maybe used in bases where the military used its own generators to generate electricity, and there were reasons to switch to 50hz if something bad happened?

Just speculatiing here. Most countries use 50 hz, so if a base has its own generators that generate 60 hz and its backup is to use power from the local grid, a switch to 50 hz would signal that something has taken out the base’s power plant. Also, clocks use the frequency of the power to keep the correct time, so even if there’s no attack (the base’s power went down for some other reason), everyone would need to know that since the base’s clocks would then be wrong.

Is it possible that the surplus people wrote up a good story to try to sell it, and the real purpose was to prevent burning up 60hz electrical appliances by accidentally plugging them into 50 hz?

Or it was merely a 50/60 hz detector?

This makes a LOT of sense to me. I just couldn’t see the logic in changing the power grid from 60hz to 50hz, but detecting the switch from locally generated 60hz power to the 50hz grid would fit.

It seems like it would be a device that would only work in some pretty specific circumstances, but maybe those situations would have been more common 40+ years ago.

Great ideas, thanks!

That’s quite possible too. I kind of remember the description talking specifically about detecting a wartime situation but I suppose if you were a surplus place that bought a pallet of these things, your marketing might get exaggerated. :slight_smile:

That would also go along with Mdcastle’s theory of keeping people from blowing things up by detecting the wrong frequency. Maybe you were supposed to plug this box in before plugging anything else in to warn you to not plug in your sensitive 60hz devices.

This might not be much help, but when I was in Vietnam, our electricity at Army base was supplied by a diesel-powered generator. It was intended to be 60 hz, but it was monitored by a local watching a frequency meter. He often thought it was running too hot, so he let the speed (and voltage) drop a little. This meant the clocks ran horribly slow, refrigerators labored[sup]*[/sup], and our nightly movies sounded odd. Once I figured out why, I would run over to the generator shed and yell at the operator, but I guess knowing that the frequency was off from an alarm would have been useful.


  • This was more serious than you might think. Without cold beer, how are you expected to fight a war, especially an unpopular one?

We know how the device behaves at 60, and how it behaves at 50, but what was the threshold in between? If it only triggered at 51 or below, or even at 55 and below, it might not be useful for Musicat’s situation.

I like this theory. Maybe the original purpose was to detect a drop from 60hz, just not because of the catalog’s theory of alerting you to WW3. In the Vietnam era, electronics didn’t have the sophisticated switching power supplies of today that convert a wide range of juice from 100v-240v @ 50 or 60hz. Then again, that era had a lot of vacuum tubes that would probably deal with those fluctuations better than the solid state stuff we have today.

Never underestimate the power of beer.

It almost sounds like one of these:

https://en.wikipedia.org/wiki/National_Emergency_Alarm_Repeater

it was a pre Emergency Broadcast System method of warning the nation of an emergency.

I bet that was it! That exact box doesn’t look familiar but since there were multiple manufacturers, there were likely a lot of different designs. And the 50hz / 60hz thing was either “marketing” on the part of the surplus company or something that I just didn’t remember through the years. If that’s the box, it wouldn’t have done anyone any good in the late 70s.

To be fair, lots of the surplus stuff at that point wasn’t really useful as is. Most of it was equipment that was waiting to be a donor for some DIY project.

Thanks allyn! I can now sleep at night knowing that I’m not missing some essential piece of WW3 early warning gear!

Or, the company found some 50/60Hz warning boxes, and guessed that they were NEAR boxes.

In Aus, US communications ran on 110 / 50Hz, so that the equipment could be standard. But the rest of the country runs on 240 / 60hz. Even after you adjust the voltage, a lot of stuff wouldn’t work correctly, and it was a constant problem for American personnel.

And factories that had backup-power generators sometimes had frequency-indicators at the switch box, so that you could see if you were running fast or slow.

You have your freqs backwards. Australia uses 50hz. U.S. uses 60hz.

Bases just use power from the local grid. So all the U.S. bases in Europe, for example, run off 220-240 volt/50hz power. Many of the buildings, especially the housing units, will offer 110-120 volt power outlets as well, but those are just coming from stepped-down voltage converters somewhere. So, it’s still at 50hz, and a lot of U.S. electronics will not work.
A base that actually has backup generators is going to set those generators to operate on the same voltage and freq as the main supply. Think about it. You have a bunch of electronics plugged in. Many of these electronics can only function properly with a specific voltage and freq. Now your base is attacked and you lose primary power. You wouldn’t want your backup generator to come on and produce a different voltage/freq. Especially at a time like that when you really need your equipment to work.

And bases that run their primary power off generators are not going to use the local grid as their back up. They’re going to use back-up generators. After all, there was a reason they weren’t using the primary, local grid in the first place.

That would make sense too. I can’t trust my memory and wish I had kept a few of those old catalogs as a history lesson for my nephews who are into tech. To your point, it seems like maybe they were 50/60hz detectors that got described as that plus the NEAR alert bit.

I don’t really blame the surplus company. Back in the late 70s, there was no Internet to research this stuff. Nor any SDMB to ask.:slight_smile:

To this day, part of Japan is 50 Hz and part is 60 Hz. Microwave ovens have a map-diagram on the back and explanation of how to set the proper switch for your location. So this device might well have been intended for the occupation, and later the military bases of, Japan.

As I recall from experience. When I lived in Spain, I recall many years ago that a friend had brought over a record player from the USA, and even with a voltage transformer, the records sounded wonky because of the difference in frequencies 60hz to 50hz. Also any apparatus with a filament like an oven or a toaster or a hair dryer would not work to spec with a frequency change.

Nichrome wire heating elements like what you typically find in a toaster or hair dryer don’t really give two hoots about the frequency. It’s simple resistive heating. The voltage matters, so you’ll usually fry the toaster or hair dryer if you don’t have the step-down transformer, but the frequency shouldn’t matter.

If the hair dryer has a synchronous motor, then, just like the record player, it will spin at a lower speed, resulting in less air blowing.

Hair dryers and toasters are relatively high current devices, and many voltage converters can’t handle the current required. Depending on the design of the voltage converter, it might just put out a lower current (and voltage), resulting in the hair dryer or toaster putting out less heat, or the voltage converter might blow a fuse, or, if it’s really poorly designed, the voltage converter could just catch fire and go kablooey.

No real issue with hair dryers, like ecg says. As long as the converter can handle the watts. The strange one that I’ve found is hair clippers. The small motors do not work well at 50hz. The clippers will operate, but they are super loud and quickly break.

The part of the Japanese power system built by the USA runs at 60 Hz, the part built in Europe runs at 50 Hz. When differing systems share power, they must alter the frequency.

Just relating my experience with american devices used in Europe with good voltage converters