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Just wondering if there is any hardware device that when it loses power, will send a remote signal to another power switch to turn off? This is more for media equipment, but I figured if anybody knew it would be here.

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closed as off topic by Kamil Kisiel, Oskar Duveborn, Mark Henderson, John Gardeniers, womble Nov 9 '09 at 4:45

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Do you mean you want to send a software signal to shutdown gracefully? Or do you want to immediately remove power for the second system if the monitored power is lost. – Zoredache Oct 5 '09 at 6:51
Like I said, it is for media equipment .. I have a subwoofer behind my couch that I have run the RCA cord to, but it stays on even if I shut the receiver off. The receiver has a plug on it which sort of acts like a switch, so when power is lost to that 'device' I want it to send a wireless signal to power off the subwoofer. – esac Oct 5 '09 at 15:56
This doesn't really have much to do with system administration... – Kamil Kisiel Nov 8 '09 at 18:03
up vote 1 down vote accepted

Depending on your need something like this might be helpful...$ja=tsid:11518%7Ccc:%7Cprd:10674532%7Ccat:Accessories

When power is no longer drawn through the 'master' socket it cuts power to the others.

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It's also the first thing that came to my mind when reading the question. Another link… These are common in power-tool/shop-vac applications... I'm not sure how well they would work for AV equipment. – Chris Nava Oct 5 '09 at 15:29

Sure, it's called a relay.

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Can you explain more? How would this work wirelessly (what I meant by remotely). – esac Oct 5 '09 at 6:15
If you mean wirelessly, then say wirelessly, not remotely. – womble Oct 5 '09 at 6:56

Of course there are such devices but you would be best off talking to whatever companies supply electricians in your part of the world. They will, or at least should, be familiar with this kind of equipement, which should be listed in their supplier catalogues.

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You have to build it the other way around because when the relay loses power, i has no power to send a command to inform another switch that the power is lost.

In TV stations, there often are tally relays that work this way. When the power goes out, a relay will send GPI pulse to a server which is configured to do something when the pulse comes in. You could just use a smart switch (i dont know if such commercial device exists, but its pretty simple to build one) which supports GPI to turn off when the pulse comes in. You have to also add a second power supply to your relay so that it works during power failure.

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Your two paragraphs contradict each other. Anyway, it's trivial to use a capacitor to store enough charge to power a radio transmitter to send the shutdown command when power is cut. After all, we're only talking about a couple of seconds max. – John Gardeniers Oct 5 '09 at 8:34

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