Dumb and Dumber:

[rattus]

While wasting time watching cable TV, someone made the claim that you can obtain enough power from a phone jack to operate a small CFL. Yes, with the conventional local loop, 50Vdc or so appears when the phone is on-hook. But, as soon as you draw a few mils of current the CO recognizes this as an off-hook condition and provides dial tone. If you don"t dial, I think they disconnect the line.

Even dumber, they said you could use a bridge rectifier to convert the DC to AC! But. they didn't specify the frequency!!

Anyone know of any still dumber claims?

 

[LarryFine]

I saw that, and PJ and I instantly critiqued the (expletive) out of it. (TiVo is great!)

It was an LED light, and he said it required AC, but the phone jack put out DC.

The only thing a bridge rectifier would do is make the load input-polarity insensitive.

 

[SG-1]

The boss got eat up by the phone line one day. He had the stripped ends in his hands when someone called his extension. Many colourful metaphors were flying.

I know you can light up a manager with the phone line.

 

[winnie]

Yea, I was thinking that the ring voltage might be enough for a small CFL.

-Jon

 

[One-eyed Jack]

The boss got eat up by the phone line one day. He had the stripped ends in his hands when someone called his extension. Many colourful metaphors were flying.

I know you can light up a manager with the phone line.

The ring voltage is 90 vac 16-66HZ. This was for the old style dial phones. Since there are still quite a few still in service I would think the volt/freq would be the same.

 

[rattus]

Yea, I was thinking that the ring voltage might be enough for a small CFL.

-Jon

Yeah, but it is intermittent! One could only read in spurts.

 

[steve66]

I'm not sure exactly how much current a phone line provides. It used to be standard throughout the country back when Ma Bell was still intact, and the phone company had to guarentee X "ringer equivalence units" for every service. Then if you put too many phones on your line, there was no gurantee the phone would ring when someone called. (That was easier to do back then when every phone had a solenoid that rang a bell.)

But now I think the phone companies are free to limit the current as much as they want.

But anyhow, lets assume the phone line would drive a 13 watt CFL. That would give you 1 kilowatt hour about every three days. At 10 cents per KWH, that is going to give you about $1 worth of free power every month.

Not very much considering you are probably paying at least $20 a month for the phone line.