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As mentioned in the "12 volt house" idea, it might be useful to have a separate DC power system in a home. Well, such a thing already exists to some extent.
I mean the phone lines that run to several rooms of the house. These carry their own power so that phones can work independantly from grid
power.
I don't know how much voltage or power you could get from the phone jack, or whether plugging in electronics would disrupt phone service.
12 volt house
12_20volt_20house
idea about DC power as mentioned above [discontinuuity, Nov 05 2005]
Telco powered products
http://www.sandman.com/telco.html
[Shz, Nov 06 2005]
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I don't think you could get much power, and I think it's only available when the phone is in use. I read somewhere that the ringing voltage is the biggest, and is pulsed to allow the wires to cool off. |
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Which brings up the possibility that the phone companies could open up their lines for supplying limited power as suggested during an emergency. If that was done, using the phone should still be possible, perhaps with a special adaptor. I know that there are internet access suppliers that use the phone lines and that say regular phone service continues. |
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I dunno what electronics would be useful, though. Why power a radio if the phone is working? |
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I like the connection of ideas. + |
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The voltage on a phone line varies by country. It can be tapped (stolen), but there’s very little amperage to work with, so applications are limited. Unfortunately (for [rr]), this is baked, however, there is good news for [jsp] - see link. |
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I've seen mouths run on off phone jacks. |
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+ Shouldn't be too hard to build one of these. Not that
you'd connect unapproved equipment to the phone lines,
nosireebob. |
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You probably won't disrupt anything, but the phone provider typically current-limits the phone line to about 10mA or so (don't remember the exact number, but it wasn't much). It's enough to run the basic phones which don't need a separate power supply, but nothing more. 10mA at about 20-ish volts or so, iirc translates to only 200mW, or 1/5 of a watt. There are some uses of this, and I've seen some creative DIY projects which exploit this, but you're probably not going to be able to power many things on the phone line. |
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Could you use the phone lines in your
house as an internal distribution
network at >200mW? Just feed 20V in
at some point (sorting out all earthing
and referencing issues) with a higher
current limit, then you could take it out
at any jack in your house. |
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Not much use in a powercut, but it
would give you multiple 20V, useful-
current outlets around the house. |
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Sounds like a good idea, and you certainly could but with quite a bit of modification. First of all, you have to remember that you still can't put too much current into the system, since the phone lines can't carry that much current (without setting things on fire). Additionally, the voltage changes depending on the call state (I think there's a signal for voicemail, etc. . .) The main thing you'll need to do first is some way to isolate your power from the phone company's power--you don't want to backfeed your own power into their system and fry their equipment. Then you'll also probably have to account for the different states of the phone line, and the fact that you'll have to carry both AC (your voice signal) and DC along the same line. |
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Now that I think of it, it's almost like recreating PoE (Power over Ethernet), except on phone lines. |
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