Mr. Rawles,
I found this web page interesting: Free Hidden Electricity.
Essentially this site has provided some basic information on how to tap the small amount of electricity available in our land lines to use for charging batteries or powering a lamp should the power go out (and not the phones) in a small emergency scenario.
Within the discussions that follow the post are some legal and contractual concerns and a link to a retail lamp product you can currently purchase for this application. – Tanker
JWR Replies: There are some ethical issues raised by this Instructable video, since telephone service contracts are not contracts to purchase power–however miniscule the amount. But beyond that, there are also legal issues. If someone were to leech too much of the current from their phone circuit’s “on hook”, “off hook” or, “ringing voltage”, it eventually would be noticed by your phone company. Read your phone company service agreement carefully before improvising or purchasing any such emergency device!
One follow-up post from “Myself” summed it up nicely:
“This might be useful, if it was actually running that big lamp shown in the photos. Phone lines are fed with “talk battery” of 48 volts, and are current limited somewhere between 20 and 80 milliamps. A large portion of that limit comes from the resistance of the local loop, so as your current draw goes up, your available voltage goes down. You’ll be able to suck about a quarter watt from most phone lines, if you’re lucky.
Of course, going below 600 ohms of loop resistance (your circuit looks like a dead short to the phone company) will cause the switch to think you’re “off-hook”, which is to say, you’ve picked up the phone and are ready to make a call. It’ll send dial tone, and when you don’t dial anything within a few moments, it’ll send off-hook warning tone, and after a few minutes of that, it’ll disconnect your line entirely and generate a trouble message. This means you lose talk battery and phone service.
Once that happens, the switch will periodically reconnect your line to see if the trouble has been repaired. If you leave your “circuit” (and I hesitate to call it that, did you even read the LM317 datasheet? If so, improve your Instructable by explaining its function!) connected for too long, you’ll either get a knock at the door, or simply find yourself without phone service for a long time.
Since this gadget violates about half of part 68 of the FCC rules, you’re not allowed to connect it to your phone line. They won’t throw you in jail for it, but I’m pretty sure they could confiscate your toys and laugh at you. I’d be truly surprised if anyone levied fines against a clueless kid with a soldering iron, but stranger things have happened. (I am not a lawyer.)
Incidentally, this concept is so old, and so laughable, that telco-powered products are a staple joke in the industry. Congratulations on joining the prestigious ranks of Dr. Drizzlenik and others who’ve discovered this revolutionary “hidden” source of power!
P.S. A five-dollar solar panel will produce more power, more cleanly, and is portable.”