Introduction: Phone Line-powered Flashlight

Picture of Phone Line-powered Flashlight

What do you do when the house power goes out? Look for flashlights! But if you're as sloppy as I am, you're going to see that they are out of batteries since the last time the power went out.

Since, in 90% of the times, the phone line is still working even when the whole city has no light. This instructable will show how to make a flashlight that uses the phone line power. (Yes, the phone LINE delivers a small amount of current to your house)

Before I start, I'd like to say that I did not find anything forbidding me to plug this into my phone line, but you should check whether it's legal in your country and if using the phone line current is prohibited by the phone company's contract. (and take it easy on the comments. English is not my first language and this is my first instructable)

Don't forget to rate!

Step 1: What You Need

Picture of What You Need

The materials to make the flashlight are:
1x Phone wire
1x Box to put everything inside
12x White LEDs (3.0V / High Brightness)
1x LM317L or LM317T (Voltage Regulator)
4x IN4007 (Diode)
1x 6.8K ohm resistor
1x 270 ohm resistor
(the 2 resistors values may change depending on your phone line - See step 4)

Sorry for the picture, I've made this project a couple of years ago (way before I found the Instructables website) so everything is already put together.

Step 2: Soldering It Together

Picture of Soldering It Together

So this is the schematic for the circuit.

My phone line delivers 48V DC and something around 20mA, and when the phone rings, it delivers 96V AC.
This works in a way that the phone line won't stay busy while the LEDs are connected and when you pick up the phone, the light goes off and allow you to use your phone normally.

-Solder all 12 LEDs in series (negative pin of a led to the positive of the next led)
-You will use the four IN4007 to make a Bridge Rectifier.
-Solder the negative pin of the last LED to the negative pole of the bridge and solder the positive pole of the bridge to the input pin of the LM317.
-To the output pin of the LM317 you will solder the 270 ohm resistor (R2), and to the adj. pin you will solder the 6.8K ohm resistor (R1).
-R1 and R2 will be soldered in parallel and then to the positive pin of the first LED.
-In the middle of the Bridge, where the ~ signs are, you will solder the RED and the GREEN wires that comes from the phone wire.
(The bridge is necessary to rectify the 96V AC when the phone rings)

Some phone wires have 2 more wires inside (yellow and black), we won't use them here.

Note: The third image is the schematic I got from LaserDave, I promissed I'd post it up, so here it is!
A want to point it out that I have not tried to build it from his schematic, so if you have any question look him up.

Step 3: Put It in a Box

Picture of Put It in a Box

I found a little plastic box to put the circuit in. I punched holes on a white cardboard and glued it on the opening to keep the LEDs in place.
It doesn't look good, but this was my first electronic project and I didn't know anything about it.
It will look good if you use a perfboard to solder the LEDs and even better if you find a 12 LED flashlight with a reflective lid to mount everything in.

I drilled a hole on one side of the box, put the phone wire through it, tied a knot and put glue on it so if I pull the wire, it won't break the red and green little wires.

Step 4: Test and Adjustments

Picture of Test and Adjustments

You're done, just plug it in the phone line and enjoy! (also works with DSL lines)
It's not like a 100W light bulb, but it's perfect for when the lights are out!

These settings will give you a very bright light, but in some cases you might get busy line on your phone.
To fix that you can change the R1 and R2 resistors.

The higher is the R1 and the lower is the R2, the brighter is the light. But it's more likely to get busy line.
If thats your case, you can put a higher R2 resistor (330ohm).
If you still get busy line, put a lower R1 resistor (3.3K ohm or 1K ohm)

If you don't want to test a bunch of different resistors, just stick with R1 = 1Kohm and R2 = 270ohm. This will work for sure, but you will lose a little amount of brightness!

Any question, just leave a comment

PS: -I don't know if this is legal or not in your country, you should check it out yourself, please don't flood the comment page saying that this is illegal as if the World were ruled by your country's laws, because it's not!!
-I've built this and it works perfectly. I receive and make calls at any time when this is plugged to my phone line, no interference at all.
-Also, if your phone line is equivalent to mine, you don't have to change anything. If you really think any component is not necessary, give it a try and post the instructable so we can learn from it!

PS2: I am not incentivizing anyone to "steal" energy from the phone company. Use it with intelligence! If you keep it plugged for the whole day and 1000 people from your city do the same thing, the phone company will start charging for this energy and everyone loses.


hohum (author)2016-07-09

i see what you did in regards to the LM 317L, the output of the 317 is +, on the printed schmo, you have the op going to the cathode, i think the op should be going to the anode- please check


hohum (author)2016-07-09

the 4 diode bridge seems to be reversed per the hand drawn schmo and the printed schemo??

MazenS (author)2016-01-17


nikosg2 (author)2015-11-23

very good. thank you.

Wasiuddin (author)2013-02-02

Thank you, with this idea, I am running my stereo, computer, refrigerator and 2 savors, i cook my food in an electric oven now, man its awesome (i mean idea),
only thing I couldn't figure out till now is how to market it!

Kadil001 (author)Wasiuddin2015-09-13

Hi how can I contact you. Can you please mail me on

asad.amin.7547 (author)2014-12-21

can you made it from me. i am from Pak.

1024 Web Solutions (author)2014-08-21

So this is going to be a dumb question, sorry. I use VOIP and stream my TV, but I pay for Internet from Comcast (8ms ping 58 down / 11 up 98% of the time) Comcast also provides my phone service if I used their modem or pay for it. Question is, for emergency purpose only, if I use the land line wall jack to provide light or emergency calls, does that not constitute appropriate use in the USA?

romarlo (author)2014-07-13

In the first schematic the leds are in the right polarity, but in the third image it looks bad

kmekky (author)2013-10-10

hi thanks for the idea now can u add a part to your project to make ur device senses that the current was cut off and light automatically ?

Nightshade (author)2013-09-22

how can i use the phone line to charge my iphone. I dont have a land line and I know there is power running through the wires even though I dont pay for it. Would I have to use a transformer to step it down. What is the voltage coming out of a wall charger for an I phone?

alpist (author)2013-08-13

Hi! The phone line delivers 54.5v and when the phone rings 55.3v.

Should i do something different?

Thx, Obrigado.

art.z (author)alpist2013-09-09

Hi alpist.
It should work just fine. You can always change the R1 and R2 resistor until you get the desired effect on the LEDs.

madhurirao (author)2013-03-25

hello.. u sadi that ur phone delivers 48 v DC n when phone rings , it delivers 96 v AC.. right..! can u plz explain how dis hapend??????? r else send me a link twhich related to this ....! as soon as possible
thnku !

kfattoum (author)2012-12-22

is there any alternate for the(Voltage Regulator)

kfattoum (author)2012-12-21

what if we have already 14 LEDs in a circuit ??

SPORTIDEANTA (author)2012-11-28

quiero ver video youtube, como saber luz como parpadera o continua luz, me duda, soy persona sordo, necesita flashlight

ZaneEricB (author)2012-09-14

I have 8 pre-made LED circuits in the form of a circle which are currently connected to 3 Dcell batteries each. This was a marketing lamp in its former life. There are about a dozen LED lights per circle. How would I attach the phone line to this so I can not use the batteries?

Would it be as simple as attaching the phone line to the +/-?

AndyPipkin (author)2012-02-21

illegal/criminal as far as I know!, check with your phone company, you can be cut off for stealing power.

Biscuitus (author)AndyPipkin2012-05-11

It's not. They are required by law to keep that voltage on there for 911 purposes. And it's not like you're powering a refrigerator. What qualifies me to say this? I worked for Bell South, I was the guy that installed the OC182's.

AndyPipkin (author)Biscuitus2012-05-13

....And being able to run some cable does not qualify you in legal matters! lol

OCPik4chu (author)AndyPipkin2012-08-28

Ya know, saying 'as far as i know' doesn't exactly qualify you in legal matters either...

Part 68 of the FCC regulations states that any device that connects to the phone line and is not actively communicating must present a resistance of at least 5 MΩ and a device's continuous-current drain must not exceed 10 µA.

That being said, Biscuitus is partially correct. The voltage is there for a reason and is required to be there but that doesn't mean you have the right to use it for your own means. When you sign your agreement with your phone company it is for telecommunication service, not for power. 99% of the time I bet there is going to be a clause in your terms of use that says you cannot draw power from the phone lines for non telecommunication use, etc, etc. So go read it before you make assumptions. If you are using the power off a phone line often it can be seen by the carrier (it will look like a bunch of hang-ups/pick-ups to the system) and it may raise concern so keep that in mind as well if you choose to 'do it anyways'.

So, that being said, its technically not illegal but you may not be allowed to do it based on your service provider. If you want to use it for emergencies great but don't start trying to charge batteries off your phone line or something. Also, this likely only works if you have analog phone lines if you have digital or phone via cable I would be more careful trying this as you could damage something.

To the OP, this is still as nice instructable and for emergencies this is a great device and has some real potential. If I was looking to take it to the next level I would take this design and apply it to an outlet based battery light, one that charges via a normal power socket, with a battery, but had the option in emergencies to run from the phone line too. But a +1 for you regardless :)

AndyPipkin (author)Biscuitus2012-05-13

I didn't say they didn't have to keep the voltage there, it makes the phone work, you are just not meant to be stealing it, the same goes for turbines running off a water tap.

luxstar (author)2012-08-26

In light of some of the problems with this solution to emergency lighting I offer this humble solution as an alternative:

Or this:


whisp3r3r (author)2012-06-11

cool :)... will it be possible to connect readymade LED torches(10+LED bulbs) to phonelines somehow?

nodoubtman (author)2012-02-18

Now i have this at home! :)
Thanks! :)

raza896 (author)2012-01-16

Hello. Art.z I am Kashif Raza from Pakistan. I read your instructable and it is awesome. As you guys know that in Pakistan the situation of electricity is very bad. I am a student and I think this idea ( to build a Phone line powered LED lamp) is a best alternate in Load-shedding hours. But i have a problem with a part LM 317L. What is this and how can I get this part from market or from any old electric board. Any idea please. Reply me as soon as possible because exams are very near.

usbg3rd (author)raza8962012-02-02

salm kashif m umer .from pakistan

lm317 is a voltage regulator and u can get it from college road in rawalpindi near commetiee chowk.

for further information on lm317 read its datasheet u can download one from

raza896 (author)usbg3rd2012-02-02

Thankx umer for your kind reply. I have just one confusion that how to ask to shop keeper for lm317???? And im from Lahore and im sure if i know how to ask for lm317, I can get it from Hall Road Market..... And What to do think about this instructable? Will it work in Lahore with PTCL phone line????

usbg3rd (author)raza8962012-02-04

k will tell u on private message as it is not related to the instructable

raza896 (author)usbg3rd2012-02-05

Thankx I'll wait.....

fazgard (author)2011-08-14

And the last Hurrah - since I've been drawn back into the discussion - and I'm trying to be very nice.

It's the FCC part 68 that governs this in the US. Do not put devices like this on the phone lines for many reasons covered below by responsible people.

And here is a great compliance article on the subject that will be a great education for anyone interested in connecting things to the pots (Plain Old Telephone Service) lines that are coming into their house.

Cheers, and with that I'll sign off!

ragman_ar15 (author)2011-06-18

Wow alot of improper info here. Fact is I have removed a device very simalir to this one from a home on a service call. not only did it cause a very minor fire, it also acted as a disturber on a several uverse loops in the area, the individual who did this may be fined several thousand dollars on top of the $171. 00 repair bill. and It did cause his DSL to run very poorly. DO NOT add this kind of device to your loop! Full disclosure here. I am not sure If it was the device or the lightning strike that started the fire, but the damage was localized to that jack. 2 other techs zeroed in that home being the cause of the uverse failures that all work flawless now that it has been removed. maybe the engineer can explain the interference issue better

fazgard (author)ragman_ar152011-08-14

@Ragman - thanks for your real-world experience, that concept is what I was referring to earlier - and got bashed by LaserDave.

I think that anyone that puts something together like this and ties it into a POTS line is silly, and inviting disaster on multiple fronts..

I work on the mobile backhaul and transport side of telco, and don't have the local loop experience in troubleshooting problems to the CPE so thanks for proving the point.

I'm not doubting the electronic engineering - built many circuits myself over the years - yes, it does 'work' - but if not done properly (UL Listed devices) it's asking for trouble.

@everyone else (including mainly LaserDave) -
1. it's great to learn how to 'build things correctly.
2. It's never correct to hook home made projects up to the utilities (including our pots -48 vdc)


ragman_ar15 (author)fazgard2011-08-14

Just a week ago I read online about a power worker who was killed by a homemade transfer switch used in line with a generator during a power outage. It was not mentioned if charges were going to be pressed.

fazgard (author)ragman_ar152011-08-14

Back feeding a utility with a home made transfer switch is an extreme (it does happen here in Florida a lot) example of the concept - but is a perfect example of it. - No one should hook up anything not designed for hookup to a utility.

This is literally a 50 year old discussion (yep, it's been around longer then that) ..

After the posts last night . .I thought more about it, and could you imagine if multiple people did this in developing countries where the infrastructure is not as robust and they were using old switches ...

Again, worst case scenario - but the main idea is there's other ways to get power then draining the -48 from the batteries in your local hut.

Cheers, mate - gonna write this one off!

ragman_ar15 (author)ragman_ar152011-06-18

Oh yea Telcos have alot more loot than most of us do, and dont think they will not hold you to the wall if something you have done causes any damages to a network.

LaserDave (author)2011-06-18

Sorry to have to post again, but I just don't understand why Colin55 is so rabidly against this. As art.z has stated, the circuit has been built and works perfectly. I also built it two days ago just to prove that it WILL work, and just like Art.z it works just fine and so does the phone operation.

@Colin55 -- I don't know what has blown your skirt up, but the LM317 IS required to keep the current on the LEDs constant. The circuit in this 'ible needs to be changed slightly as mentioned in my earlier post, but it will allow the LEDs to operate properly even when the phone rings.

NO, the LM317 will NOT be damaged when the phone rings because it's in SERIES with the LEDs with no reference to ground. This is called "FLOATING", and the regulator will see less than 6v once it goes through the loop. You DO remember series circuits, don't you? This is how Christmas "mini" lights used to work - a group of them in series allowed 6v lamps to work on 120v. In this situation (once the schematic is slightly altered) the regulator sits on the line and varies the current based on the voltage drop across the main resistor. It NEEDS to be there, and so does the bridge to protect the circuit from the 96vac RING voltage. Do you not like the LM317 or bridges? Are they hard to get where you are??

This circuit isn't "absolute madness" and to "avoid it like the plague" - where are such comments coming from and why so bitter?? Nobody asked you to include this circuit into your eBook, in fact advertising your stuff in someone else's instructable is pretty lame.

And finally - it is NOT illegal to put something on the phone line that draws a small amount of power, so long as it isn't loaded down to the point of tripping the "off-hook" sensing. Novelty phone items have been powering their circuitry off the line for YEARS - this is no different!! Would you agree that a short-circuit would be the most extreme condition for a phone line? Would you think such a thing would be permissible? Well, this very thing occurs and HAS occurred for decades - rotary-dial phones short the line multiple times for each dialed number (quantity of pulses equal the digit being dialed - ie: #6 = six pulses).

I've sent the author (art.z) a schematic that WILL work off the phone line. He will put it up because this site won't seem to let me upload an image with my comment. Since different phone company's sensing current varies, this circuit will work with most systems. The bridge (or 4 diodes) will rectify the incoming voltage and change the ring-voltage AC into DC, then limits the current going into the string of LEDs to 12mA, so high-brightness LEDs will be quite bright. This circuit works with any number of LEDs and any voltage input of any polarity. (Of course the input voltage must be enough to satisfy the number of LEDs you choose. ie: 4 LEDs = minimum voltage of (4 x 3.4volts = 13.6v) or 12 LEDs need a minimum voltage of (12 x 3.4volts = 40.8v) which is straightforward).

*** Note: I have this exact circuit operating on my own phone line, and it has been running since this article came out. It works PERFECTLY. When the phone rings, the LEDs do a nice gentle flickering - PERFECT for the hearing impaired. ***

ragman_ar15 (author)LaserDave2011-06-18

no expert here but if you make a mistake and somehow compromise a telco network you are in fact breaking the law, and in the u.s interfering with homeland security. It is best not to add something that is not fcc approved to your loop. That being said in the 80s it became legal to add anything you wanted to you phoneline as long as it does not interfere with the normal operation of the network . This could in fact do just that. If it is not done properly.

LaserDave (author)ragman_ar152011-06-19

I agree with you completely - which is why I provided a schematic (via art.z) that shows the proper values to use in order to preserve the functionality of the telco line. I wouldn't want anyone to trip their "off-hook" and then have an emergency where they couldn't use their phone.

While I would personally RATHER that people don't even bother with the line and use solar or some other alternative, I will still fight for people's rights to learn how to do it correctly. My point of view is that the topic has come up, people are guessing about how to do it with many variations. Since I am an engineer, I felt that it was best to show how to do it correctly and to avoid creating problems for themselves. In other words, if they are going to do it anyway, at least do it right.

One thing I'm not clear on, is how a personal phone line (residential assumed) being compromised has anything to do with "homeland security"?? A residential POTS line is always at risk for short circuits, rain, crushed cable, bad equipment (this would apply here) - but it never has any effect on the Central Office since each line is separate and won't affect another. In fact, no matter what torture you can bring onto your line, there will be no effect on any other in the trunk system whatsoever. While I am really sick to death of hearing how everything affects "homeland security" in one way or another, I am curious to learn if there is something to this and maybe you are aware of something I'm not.

Thanks for your comments. Have a good one.
~ Dave

ragman_ar15 (author)LaserDave2011-08-14

Just a couple of days ago pres Obama visited Holland MI. The secret service needed several pots Telco lines for Security reasons. They do not rely on even there own secure wirelwess network for most communications, but Wired Telco. Extremely secure. This is just one example. I have not had a chance to look up the letter I mentioned to you earlier. I am on vacation in 2 weeks and will have time to go thru old emails then.

ragman_ar15 (author)LaserDave2011-06-19

A central office line card may contain up to 4 separate carriers. depending on slic 96 fiber to the node etc. A sever enough fault could cause a line card to fail completely. or in the event of a t1 up to 24 lines. interfering with other loops. Keeping others from reporting an emergency. Even cellular service depends heavily on the wired networks . The telco networks and it employees are deemed an important part of home land security, 911, police, fire rescue, and yes even the military all still depend an the wired telco networks. Although not entirely. I wish I had a copy of a recent letter stating that interfering in any way with telco plant or employees is indeed a federal crime. The letter went in to great detail about how some acts are indeed considered terrorism one act included adding certin equipment to networks . this part was oddly enough very vauge on what it was.

colin55 (author)2011-06-16

Some phone companies detect as little as 0.25mA and this project will not allow the phone to ring as the equipment in the exchange will detect the current and consider the hand-set is lifted.
A lot of other mistakes have also been stated in the comments above. Particulary the comment that the line voltage rises when the hand-set is picked up. It simply drops to 6v to 12v.
The regulator serves no purpose AT ALL. It can be removed.

colin55 (author)colin552011-06-16

I say the regulator serves no purpose at all because the voltage on the line is a constant value.
Apart from the circuit being incorrect, as R2 is not needed, the regulator does provide a fixed current no matter how many LEDs you use.
However super-bright LEDs work on currents from 1mA to 17mA max and any current from as little as 0.25mA will trigger the exchange to detect the hand-set is lifted.
It is absolute madness to put this circuit on the phone line as the "system" can at any stage send out a test signal to ring the phone for 2 rings and if it does not detect an "open circuit" and a phone ring voltage of about 120v AC, the exchange will report a fault.
That's why your phone sometimes rings at 2AM. It is the robort testing the line.
The simple way to design the circuit is just to have a single "line diode" and a resistor to reduce the current to less than 17mA, say 10mA to 12mA and only use the device when the power is off, remembering that the phone may not ring when the device is connected. And when the power is off, this is the very time when you may want to get an emergency call.
The whole concept of this project is BAD and FAULTY and ILLEGAL and IMPRACTICAL.
It should be avoided like the plague.
It is such an absurd idea that I have NOT listed it in my 200 Transistor circuits eBook on website.

Colin Mitchell

art.z (author)colin552011-06-16

First of all: The project is done AND IT WORKS, the phone line works normally when this flashlight is plugged in!
It stays on when the phone is hooked up, it blinks when the phone rings (YEAH, THE PHONE RINGS NORMALLY), and it goes off when you pick up the phone.

Second: I cannot see how this is bad, faulty and impractical! For me this is perfect. Whenever the power is out. I can simply plug this in my phone line AND BOTH WILL WORK PERFECTLY.

Oh, "You haven't posted on your eBook"?? Too bad, apparently you've been beaten by a teenager who doesn't even know if the LM317 is NPN or PNP!
Please, the Instructables website is not the place to advertise your stuff!

And last: The voltage issue.
It was just a misunderstanding, the voltage rises to 96V WHEN IT RINGS, apparently, it drops to 6V when you actually pick up the phone! LaserDave had already posted it!

Let's make this a constructive website people!

fazgard (author)art.z2011-08-14


Lol, I keep getting pulled back into this instructible from the email system ...

Constructive is good.

Connecting devices to the pots is bad and illegal.

Sorry man, but although this works - any responsible engineer (or hobbyist) that does not point out that it's illegal and dangerous to do couldn't 'sleep at night' and if it stops 1, yes one house fire or utility interruption, well .. it's work commenting on.

>>> Buy/ build a crank up/solar charged flashlight for when your power goes out.......

DO NOT connect any non-UL approved devices to the POTS ..

colin55 (author)art.z2011-06-16

Firstly the addition of any "leaching device" on the phone line is absolutely forbidden.
Secondly, the device is not authorised. Both these incur a $5,000 fine.
Thirdly, my phone line “shuts down” when more than 10mA flows. So the circuit will not work.
And fourthly you are promoting a device that has no 5kV insulation, is totally forbidden and will not work on most phone systems.

colin55 (author)colin552011-06-16

Measure the ring voltage by adding white LEDs until they dim when the phone is ringing. Our system produces 125v AC.
The LM317 will accept up to 40v between input and output.
It will possibly be damaged the first time the phone rings as the difference between input and out is about 125v minus the LED voltage of about 50v = 75v.

t.rohner (author)art.z2011-06-16

LM317 isn't a transistor, but a voltage regulator. What you want to have for Leds, is a constant current source.

colin55 (author)colin552011-06-17

The reason why the circuit works with the regulator is the fact that it is only delivering 4.5mA to the LEDs.
This same current can be obtained by placing a 3k3 resistor and diode on the line with 10 LEDs.
You don't need the regulator or the bridge or the two resistors. They are superfluous.
The line is classified as a constant voltage and when the AC signal is super-imposed on the DC, the LEDs will increase in brightness but not be damaged.

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