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Phoneline-powered cordless phone

Rechargable phone powered by phone line
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(+5, -2)
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Simply a cordless phone charged by means of a small current drain from the normal wired phone line. I realize this is a bit of an anachronism in this age of cellphones.

The primary advantage is that the phone would continue to work in the event of a power outage, unlike most cordless phones, which require ac mains power to function.

The current would have to be minimal, in order not to run afoul of phone company tarriffs.

P.s. Shouldn't this category be 'Product: Phone Cordless' ?

csea, Jan 20 2010

http://www.engadget...urrent-if-you-dare/ [leinypoo13, Jan 20 2010]

'Phone jack powered portable blower _27Phone_20jack_20p...20portable_20blower
My version [nineteenthly, Jan 22 2010]


       People have apparently been getting power from the phone line for awhile. In the link, it says there is a "if everyone does it" concern.   

       As you mentioned: // From Comments in the link: But modern (90s) switches have mechanism to detect such abuse or faulty phone line/equipment. People get billed/sued for damages from the phone company, and arrested/prosecuted for violating relevant laws.
leinypoo13, Jan 20 2010

       //Shouldn't this category be 'Product: Phone Cordless' ?//
thinking more along the lines of "Public:Scam" personally.

       Might be an idea for an 'extra charge' (no (double) pun intended) on your monthly bill, probably 2kwh/month or so. The phone company would easily break even with what they could charge.   

       But is the circuit live when the phone isn't ringing ?
FlyingToaster, Jan 20 2010

       // is the circuit live when the phone isn't ringing ? //   


       Depending on the system, there's a notional "- 48V" DC supply; it harks back to the old Strowger tick-tock electromechanical exchanges. The SLIC senses "off-hook" when the instrument resistance drops from the 600 Ohms or so of the AC ringer coil to a much lowe value. The volatge then drops to 10V or so (again, depending on locality) for dialling.   

       It's possible top pull about 5mA from the average SLIC without setting it off-hook. That would be 48V x 5 mA = 240 mW, derating to a 5V output through a low-dropout reg, near enough 40 mA; more than enough to keep a Bluetooth-based device in good health .....
8th of 7, Jan 20 2010

       I posted this idea ages ago.
nineteenthly, Jan 20 2010

       //I posted this idea ages ago.//   

       I didn't find it in my search. Link?
csea, Jan 22 2010

       //2kwh/month// ??   

       I get 0.005A*48V*24hrs/day*31days/mo = 178 W-h = 0.178kwh/month
csea, Jan 22 2010

       //kwh// I think the combined power draw of a base plus a handset or two came up to 2-3W from house electrics; x 24 x 30 is a couple kwh/mo.
FlyingToaster, Jan 22 2010

       That's because there's no real pressure for a domestic cordless phone to be ultra low power - doesn't mean one can't be made. And yes, [21Q], there would need to be batteries in both the base station and handset. You'd probably find that the handset wouldn't be able to support a flashy backlit colour LCD either, just something very simple.   

8th of 7, Jan 22 2010

       But a non-backlit LCD, or one lit by a luminous substance which absorbed light when it wasn't dark and re-radiated them, would be viable because LCDs don't need much power.
nineteenthly, Jan 22 2010

       // a luminous substance which absorbed light when it wasn't dark and re-radiated them //   

8th of 7, Jan 22 2010

       Quite possibly, but i can degibberise it. There are substances which glow after exposure to light, which are, for example, used in clock dials and children's stickers. I was suggesting using that.   

       Edit: Wikipedia tells me i mean phosphorescent paint, such as silver-activated zinc sulphide or "doped strontium aluminate", it sez 'ere.
nineteenthly, Jan 22 2010

       Sp. phosphorescence. Quite reasonable for backlighting where the phone is exposed to ambient light during the day.   

       And a constant 5mA at 48V, used to charge batteries in handset and base, should be plenty to power a telephone for a few hours a day.
csea, Jan 22 2010

       Not only that, but probably artificial light too, particularly considering how well the eyes adapt to darkness.   

       The chief problem isn't technical, it's legal. It amounts to nicking electricity from the 'phone company, or at least that's how they look at it. 'Phones generally don't seem to need much power though, so maybe they could get enough from things like being carried around, exposure to daylight or ambient noise. I really haven't done the maths there and i'm suffering from deja vu now.
nineteenthly, Jan 22 2010

       Have you had that before, then ?
8th of 7, Jan 22 2010


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