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• Note that most phone companies can monitor current expenditures & take a dim view to you using your phonelines to power things. I have phone-powered lanterns for emergencies, but they can and will cut off your line if you draw too much power.

  Posted by: zlgeraibegnst@mailinator.com on May 8, 2005 at 8:19 AM

• I think someone stumbled across an old April Fools joke page...

  Posted by: BrK on May 8, 2005 at 9:09 AM

• Most LEDs can run well off ~3.3V at 20mA. I'm petty sure the phone line is 42 volts, so even at 23mA you should be able to power a dozen LEDs with an efficient low dropout voltage regulator.

  Posted by: AntonOlsen on May 8, 2005 at 1:37 PM

• 3.3V is a typical voltage drop for blue LEDs. Red and green is less (around 2V), white is higher (around 4.1V). The phone line is typically at about 48VDC. However, if you cause the voltage to drop too much (or draw too much power, or generally affect the line impedance any significant amount) your line will appear as off-hook to the phone company, meaning busy signals to anyone calling you (or, if you have call-waiting, the caller will hear a ring, but your phones won't ring).

  So, realistically the most you could really draw is probably about 5ma. Converting that to wattage (5ma at 48V) you get about 1/4Watt. If electricity is $0.12/KwH (this is usually a good rough number, your actual KwH quote is probably less, but then there are the taxes and other tariffs and fees that drive it up to about 12 cents), at 1/4W power that is .00024 KwH. Multiply by 12 cents and you get $0.00003 (rounded up) per Hour as your "savings". Multiply by 24 hours and then 31 days, and you get a grand savings of about 2 cents per month.

  Posted by: BrK on May 8, 2005 at 3:26 PM

• Hmmm..I had the understanding that when ring signals are sent, the voltage jumps to 100V+. Can anyone confirm this - a former telco employee told me this - maybe things have change. Can imagine the fun with electronics that could have!

  TM

  Posted by: TylerMitchell on May 8, 2005 at 7:30 PM

• Ring is usually a voltage of about 90VAC (IIRC). I forget what the frequency of the AC wave is, but it doesn't really matter.

  You would most likely have some sort of voltage regulator in place if you were to try and take this mythical power source. So, the 90V ring wouldn't theoretically matter anyways.

  Posted by: BrK on May 9, 2005 at 10:04 AM

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