Step 3: Construct a Simple Voltage Regulator Circuit

We know that the phone needs 5 volts in order to charge. But we don't know how much current it draws or it's equivalent load resistance. So we can't charge the cellphone directly from the phone line. We need to use a voltage regulator to bring the output of the phone line down to 5 volts and keep it there. A LM7805 5 volt regulator should work fine. 

To make this simple phone line adapter you will need the phone cord that we have been working with, the 5V voltage regulator and a USB connector cable with a female end. Just connect the red wire from the phone line to the first lead on the regulator and connect the green wire from the phone line to the second lead. Then connect the black wire from the USB cable to the second lead on the regulator and connect the red wire from the USB cable to the third lead on the regulator. If you can't solder the wires together (because the power is out), you can just wrap the wires around each lead. If you do this, you should bend the leads of the regulator away from each other. This will help you avoid accidentally crossing the wires.

This simple regulator circuit is able to safely convert the base phone signal into something that can be used to charge your phone. However, many voltage regulators are not able to handle the AC signal that they would receive if the phone rang. So if you are worried that you might receive a call while your regulator is hooked up to the phone line , then you may wish to add a diode between the red wire from the phone line and the first pin on the voltage regulator. This will protect your circuit from problems that may be caused by reverse polarity.


Too bad doing this in the US is illegal.<br><br>Better make damn sure its a bonefied emergency otherwise you'll be charged with theft and interference with communications systems....one is a felony.
<p>How many people have ever been charged with this for creating a parasitic draw on their own phone line? Good luck finding even one. </p>
Yup. This.
Jeez! You're such a genius.<br>Whether this works or not, I'm going to build this just to spite people like you.
What part of &quot;ILLEGAL&quot; do you not understand? I suppose you're the kind of person that prefers the term &quot;Undocumented&quot;.
only if u transmitt over the said phones lines <br>
How is paying a monthly fee for service theft?
*bona fide*
1) If the phone line is powered, you can make the emergency call on it.<br> &nbsp;&nbsp;&nbsp;&nbsp; ( As several other people have said.)<br> <br> 2) This is dangerous. Fifty volts is where volts have already started getting dangerous.<br> <br> 3) I am an electronic technician, and I would never do this.<br> <br> 4) You can keep a spare charged phone battery to use when the first is flat. (As I do.)<br> <br> 5) You can have a second phone charger in my car. (As I do.)<br> <br> 6) You can have a USB cable to charge your phone from your laptop. (As I do.)<br> <br> 7) What happens if your phone hack prevents some of your neighbours from making emergency calls on their landlines ?&nbsp;&nbsp;&nbsp; Do you want to be responsible for someone's death, just because you are too mean and selfish to take reasonable sensible LEGAL precautions for power cuts like everyone else does ?<br> <br> 8) DO NOT encourage people to do dangerous illegal things.&nbsp;&nbsp; If they do, and they suffer for it, you share the responsibility.&nbsp;&nbsp; (But I'm sure you will deny everything.)
The static electricity that zaps you when you walk along the carpet... is quite a bit higher than 50volts. I believe in the thousands!? <br><br>It is the current that is dangerous. I've zapped myself on household current (thankfully not thru the heart) and been fine. <br><br>A DC source will lock your body in a clench. AC can get you to lurch which could release the offending conductor.<br><br>This is of course not a good thing to do regularly... Interestingly enough the phone station uses batteries in a power outage. Then maybe generators after a bit.<br><br>We were told in training that it wasn't really bad to work on the wires while plugged in, but I get the feeling we should have.<br><br>If you wire it and insulate it properly then plug it in you'll be fine. <br><br>
<p>i too am a electronic tech...... and as my rule of thumb, 30 volts or above is dangerous</p>
<p>Electric fences run thousands of volts. Static electric shocks can be around 20,000 volts. Stun guns can produce upwards of 100,000 volts. It's not the voltage that kills you, it's the amperage. The voltage just determines whether or not the shock can make it through your skin. You would be vary hard pressed to electrocute yourself on a POTS line, absent some extraordinary occurrence like lightening strike. </p>
<p>I agree. A lot of so called &quot;electronic techs&quot; on here that don't know much. The voltage is far less important then the amperage. </p>
<p> You disply ignorance your self. The available current and the available current are of equal importance. Lethal current can't flow unless the voltage is high enough to overcome the resistance. There are two excellent videos on YouTube that illustrate how inane and dangerous the &quot;its the amps that kill ,not the voltage&quot; chant is. I suggest people look for them. I would list them here, but my bookmarks crashed and I yet to have to restore them all.</p>
<p>Take a sausage, it's has similar propriety to your skin, put two nail on each end. Solder some wire on the nail and plug them on anything giving power. At about 30 volt, the sausage will smoke, by 120 volt it will burn. Don't try 240 unless you want to clean a sausage puree of your ceilling.</p>
<p>A UL listed electric fence as commonly used for cattle is thousands of <br>volts. You won't get anything to smoke on it, nor does it instantly kill or BBQ the cattle. It's not the voltage that will quickly kill or burn you, it's the current. The voltage only determines if the charge can overcome the resistance to give you any noticeable shock at all. The last static electric shock you got was thousands of volts. Did you get any burns? </p>
<p>Do not trust the great &quot;University of Youtube&quot;. Careful your ignorance is showing.</p>
<p>Hold one wire in each hand and have someone call your line. </p><p>I dare you. Post back and let us know how it went.</p><p>You <strong><em>probably</em></strong> won't die, but I guarantee that you <strong>will</strong> be really glad there is a pause between rings so you can let go of the wires.</p>
<p>You can let go of the wires either way. You aren't sticking your foot on the third rail of a subway or grabbing the 240 in your breaker box. What is it about this thread that so fascinates people that have obviously never worked on a telephone line? The ringing voltage is irritating at most. The feeling is comparable to one of those hand buzzers people used for practical jokes in the eighties. If it was lethal there wouldn't be any telco techs alive today. </p>
<p>&quot;</p><p>7) What happens if your phone hack prevents some of your neighbours from<br> making emergency calls on their landlines ? Do you want to be <br>responsible for someone's death, just because you are too mean and <br>selfish to take reasonable sensible LEGAL precautions for power cuts <br>like everyone else does ?&quot;</p><p>If it really worked this way a dead short which is not all that uncommon occurrence, on an individual line would knock out other lines since the short draws 100% of available power to the shorted line. Fortunately, it doesn't work this way. The only possible problem would be on a &quot;party&quot; line and I don't know anyone who has had one of those since the early eighties. </p>
<p>As a friend of mine just pointed out - when the power is out, the phone company lines are running on batteries. So this suggestion is to use someone else's batteries because you were too cheap or too stupid to buy your own in advance. Plus, you are then draining the phone company's back-up batteries. Which means, yes it can effect your neighbor's ability to make an emergency call.</p>
I liked what you said thus i just paraphrased you.
Oh stop it. <br>If I do this, which I will, it's not going to make a damn difference to my neighbors.
<p>Yes, in a way it is. You are tying up a &quot;dialing unit&quot; and a phone line. There are only a limited number of these valuable resources - there is not one for ever line.</p><p>In an emergency, you may be preventing someone from making an emergency call, or contacting loved ones.</p>
<p>2) No, 48V telephone battery is not dangerous. Up to 60VDC is rated as Safety Extra Low Voltage (SELV) and is safe to touch. See UL60950 for definition.</p><p>3) Your choice.</p><p>7) This is no different to going Off Hook with a regular phone. So you won't block anyone else's calls. If you don't make a call after 5 mins or so the phone company cuts off the power anyway.</p><p>8) It's not dangerous but it is illegal to use telephone company power for any purpose other than making a call. See Code of Federal Regulations CFR Title 47 Part 68.</p>
It is not dangerous. There is 48-52 volts, but very little amps.
I just did this. Works sweet as. Bout time I got something in return for my tax dollars. LOL
<p>Firstly, I'm inclined to agree with many of the <strong>negative </strong>comments being made as one cannot guarantee exactly what voltage is coming down the line at any given time (e.g., an incoming ring signal), and that an average Voltage Regulator is not properly equipped to deal with higher voltages.</p><p>Secondly, while such a hack may <em>work </em>in an emergency, you may find that your cell phone is still useless because the power outage could have affected your local towers and you won't have a signal anyway.</p><p>I agree that if the landline is functional, have a standby &quot;emergency&quot; handset connected. In modern times, even if the line is officially &quot;disconnected&quot; it's still able to access &quot;999&quot;, &quot;000&quot;, &quot;911&quot;, &quot;0118 999 881 999 119 7253++&quot; or whatever the emergency number is in your country.</p><p>++ https://www.youtube.com/watch?v=HWc3WY3fuZU</p>
power outages effect less then 2% of cell phones towers a year<br>they run off generators <br>mr
<p>Maybe, but maybe you didn't know that a cell tower cannot handle more than 7 DS0 communication line simultaneous. So when everyone call, they drop the extra. Soo, basically, once 7 people are one the line, you'll get a busy signal from that cell tower.</p>
that actually is incorrect cause in my house we all have more than 8 cell phones and we are in the same house and we can all talk at once... excuse me but where did u here about that exactly?
<p>CTNS, read comment below. And a tower can have more than one antenna set on different frequency. Different company can have different antenna.</p><p>Also, you just might pick up the signal from another cell tower.</p>
and we all had at&amp;t<br>and we were all calling each other and we were in the same house<br>go back to sewing or something
it's the only tower in the area u sure have a lot of excuses
<p>Those are Analog numbers... Way more now since digital. You read an old article about cell towers maybe?</p>
<p>Everything is still analog. I won't get you a course of how radio wave are transmitted, but digital output cannot be send on a radio wave. A radio wave need to be alternating (AC) to be able to transmit. You can send a state of 0 and 1 put those will be represented by a corresponding analog wave (think MODEM, its digital from you computer to the modem, but analog after that). The only thing that allow us to have more than 7 call simultaneously is the coding. This coding allow multiple user on a single DS0 line, but you still cannot have more than 7 line active simultaneously. And no, I didn't read an article, it's my job. CTNS</p>
who are you?<br>cause you have no clue what your talking about<br>now a days the cell phone tower is digital go Google it or something<br>radio waves are not even analog anymore <br>neither tv signal<br>that's why after 2009 if u had a analog tv u had to get a special box to watch stuff on a antenna
no made may 2016
Huh?<br>_Oh, my doubts about outdated numbers was aimed at Sarah86, not your 2% statistic about the towers. I agree with you. ?
oh sorry ... I meant that was when I first saw this...<br>um I really don't think Sarah noes what she talking about
<p>Living in a country where the idea of &quot;sharing&quot; towers is totally anti-corporate and having had zero service for a contiuous period exceeding 48 hours, I would still recommend having a cheap handset connected to the landline socket for emergency situations.</p>
<p>This trick is as old as the hills, and has always presented an danger to all those that have tried it.</p><p>Is it worth your health &amp; bank account, when you get caught?</p><p>good luck</p>
<p>Yeah, cause you WILL GET CAUGHT. Telecom company watch what is happening on their network. Every line card from the public exchange has a dedicated twisted pair to one address. So whan they figure out that your particualr card has been off-hook for a few day, they will investigate.</p>
<p>This is illigal in most state accros the US and Canada. It is covered by the Computer Act.</p>
<p>While that may be true in some States, I don't care. Say the power goes out and all my backups failed for whatever reason (including me not keeping batteries charged or new batteries that discharged due to sitting a long time) and a family member needs help and doing this hack gets me help, to save them, well screw the law. I'll deal with that when it happens. I seriously doubt you would be charged, and if so, then so be it.</p><p>Are you telling me you would let a family member or for that matter, ANY human die, because it is illegal where you live? If so, I guess you will have to answer to a higher power, if you believe in such things. I use simple common sense on these things, by weighing cost/reward. Here the cost is probably zero, to a fine of some sort. The reward is saving a life. Hmmm, which do I choose? I know my answer! What's your answer Sarah? </p><p>Have a wonderful day Sarah.</p>
I agree

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Bio: My name is Jason Poel Smith I am a Community Manager here at Instructables. In my free time, I am an Inventor, Maker, Hacker, Tinker ... More »
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