Cheap alarm clock

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I just bought a cheap electric alarm clock - made in China naturally. When I plugged it in it displayed the correct time. How does it do this? Does it pick up a radio signal? The clock works perfectly. I am just curious.
---MIKE---

>> (44° 15' N - Elevation 1580')
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---MIKE--- wrote:

Does it have a little picture of a dish antenna on it? When you plugged it in did it go crazy and start spinning rapidly? If so it receives the time code from the NIST time transmitter in Boulder, CO. However, there are some that have been set at the factory and they have a battery back up time chip in them so that the time is correct from the start. Supposedly you never have to set these, but they are standard quartz movements that won't keep the correct time forever. I prefer the ones that set themselves to the NIST transmissions.
Bill
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---MIKE--- wrote:

Probably. I have two clocks like this and a watch, all battery operated, but you have to set them to your time zone. They are set by transmitted atomic clock signals and time is exact.
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On Fri, 20 Feb 2009 09:10:42 -0500, Frank

On it's way from China it went through Rome. The Pope blessed it, so it was set according to God. Since God is always right, so is the time. Now you know !!!!
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On Fri, 20 Feb 2009 08:36:47 -0500, snipped-for-privacy@webtv.net (---MIKE---) wrote:

    I have seen both radio signal and pre-set internal battery powered clocks. It might be either.
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snipped-for-privacy@hotmail.com wrote: ...

How did they know which time zone to preset it to???? :)
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And how does it deal with Daylight Savings on and off?
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On Feb 20, 2:30 pm, snipped-for-privacy@nospam.com wrote:

If it syncs to NIST, it gets a signal as to whether DST is in effect or not when it syncs. (well, it SHOULD, there is a DST flag. I guess some clocks may be pre-set for DST changes, in which case older ones will not work correctly now that we've been mucking about with it. I do know that my "Sharp" alarm clock handles DST correctly, that is, it gets its DST flag from the NIST signal not from its internal programming.)
nate
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On Fri, 20 Feb 2009 11:30:35 -0800, snipped-for-privacy@nospam.com wrote:

Many of them are having problems with that once since they recently changed the date.
The only really accurate way is the radio sync along with user input of the correct time zone.
All I have seen allow manual changes.
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    I understand they set the time based on the destination for the clock.
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snipped-for-privacy@hotmail.com wrote: ...

So you're telling me WalMart is buying, keeping inventory straight, and shipping individual lots of clocks to various time zones?
While possible, seems highly antithetical to cost-cutting ...
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The clocks I see have a switch to set the time zone.

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Mark Lloyd
http://notstupid.laughingsquid.com
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I don't know how they handle their distribution. I would think that the problem you are pointing out would explain why they often seem to be a time zone or so off.
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wrote:

We have an "atomic clock" at work. It is often off by an hour and right now it is set for a different time zone so it appears correct. When we go to DST, who knows what will happen. It has been stable for a couple of months now, but at times it would make an adjustment and come back an hour off.
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Ed Pawlowski wrote:

My "Sharp" brand "atomic" alarm clock from Target has been flawless since new. Only issues I have with it are short battery life (it's powered solely by batteries, have to replace them every couple months because the display gets hard to read at night) and not very loud alarm beep. But I can't use an AC powered alarm clock unless the alarm works when the power is off, and while some may work like that, it's hard to find documentation that it will in fact function.
nate
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Nate Nagel wrote:

I have a couple of "Sharp" brand wall clocks. They have good battery life, but of course they don't have digital displays and alarms. One of them keeps good time, almost, right through the DST change. The other one doesn't. The first one I bought apparently uses the DST flag on the time signal. However, it has a quirk that in the morning after a change it will be right, then in the evening it will go back to the other time. Then the next morning it will be right again and will stay that way till the next time change. The second one I bought of the same brand and model has the DST change hard coded, so it is off an hour during the interim between the new time change and the old one. I do usually set the time zone to compensate, but people in Eastern and Pacific time zones just have to lump it I guess.
Bill
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Nate Nagel wrote:

Forgot to mention, one more quibble. The clock I have uses a battery powered outdoor temp sensor, and apparently supports three of them. I'd love to have extra temp sensors so I could monitor temp in the attic, garage, whatever, but who knows where to buy them. I suspect that it was probably a relabel of someone else's product, but whose?
nate
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wrote:

A lot of them use a garden variety LM134. This ends up being very linear across a wide range of temperatures. (unlike thermocouples and thermistors)
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on 2/22/2009 11:17 AM (ET) Ed Pawlowski wrote the following:

Now, if they will make all time keepers with an atomic time feature, maybe I won't have to go all around the house resetting appliance clocks after a power outage. :-)
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Bill
In Hamptonburgh, NY
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wrote:

    Yea many of them were/are poorly programmed. Part of the problem was the change in DST that was recently made.
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