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AC time
Time delivered by electric utility | |
If the electric utilities encoded the time on a carrier wave on the 60 cycle power to your house, any appliance that is plugged in could automatically know what time it was. No more blinking 12:00, no reseting the clocks for daylight savings time, no flipping through manuals everytime you buy a new TV/VCR/DVD/etc.
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Difficult if you live near the border of a time zone, but just an hourly synch pulse to avoid those minute glitches would be nice. |
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Cable television does this, and most new VCRs will automatically set their time. |
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Modulating anything onto the 60Hz (or 50Hz) carrier frequency at the power station is going to be a challenge. Either you need to switch off for a cycle or two in some kind of code, or you need to adjust the phase by an amount that can be detected. The first needs a pretty bit switch to do Morse code on a 100MW signal, the second would need to (quickly) speed up or slow down a large rotating generator that weighs hundreds of tons. |
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....and then there is the issue of getting the modulated signal across each of the many transformers between the generation station and your house. |
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I once worked with an x-ray spectrometer that kept a running count of its total operating hours. It counted off an hour every 50 minutes because it had originally been designed run off of 50 Hz power. |
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My high school had clocks that did this; the modulated signal was added at the main breaker, and it would send a signal that would reset the clocks at midnight and at noon. |
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A better bet would be to connect your time keeping devices to the land line telephone. The Caller-ID signal carries the current time and date already. |
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I have a radio clock which picks up a timing signal from long wave radio (atomic clock in rugby). It sets itself, date and time within a second in millions of years. Daylight saving time too. (BST) |
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i believe that the TV and Video clocks tap the time from teletext or atleast that is what i remember form the salesman's spiel when we bought them. |
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You'd have to create a filter to hook up in front of any devices that might be upset by the extra signal. It depends on what kind of modulation we're using, but I'd imagine that not all electronic devices in your household would handle the extra information without doing something funky. |
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I also have a radio atomic clock, the signal comes sometime at night from the States (supposedly the RF interference from cities is much less at night and the signal can be reliably broadcast at lower power). Got it at Radioshack, great idea. I like the power cord idea better though, because it could set the time the instant you plug it in (rather than waiting overnight). For my clock I have to tell it which North American time zone I am in, there could be a switch like that on whatever device has the clock. Every daylight savings time I have to go around and re-set all the clocks, why can't somebody make that easier???? Gosh! |
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