Automatic Telephone Recorder

[James Bond] types and those suffering from a hefty dose of paranoia can now record all telephone conversations. [Trax] built this module that monitors the phone line and starts recording when a handset is picked up. A computer does the actual recording, triggered by the microcontroller via a USB connection.

We like the use of an old PCB for a faceplate, we’ve certainly got some duds of our own sitting around. The three cords are a bit confusing though. One for the phone line, one for the USB, but what does the third do? Is it an audio-out connection?

We’ve asked [Trax] to post a schematic and source code if possible so that might clear up the mystery.

Update: [Trax] let us know that there is a red button with white lettering at the bottom labeled “download”. This contains schematic, code, pcb layout, and PC software. We just missed it the first time around.

40 thoughts on “Automatic Telephone Recorder

  1. I’m pretty sure the phone line is looped through, hence the third cable. You still have to have a phone somewhere in the system, after all, or there wouldn’t be anything to record…

  2. Judging by the component layout (bridge rectifier and transformer), I would say that the RJ-45 is for external power.

    Why run external power when the USB +5V would suffice?

  3. The three lines are:
    -phone line in
    -audio output
    -USB output
    These are directly labeled in the schematic which is posted in the .rar file which is available near the bottom.

    @Saydrah: Actually, it does not need a phone out. The way landlines work is such that this would just be sitting connected to one jack, and someone could use another phone in the same house, and it would hear the whole conversation.

  4. hi,
    the cables are:
    RJ45=tapped phone line
    white=audio out, to sound card input
    and no, you cant use voice modems because they can’t sniff audio from the phone line without “taking the line off-hook” therefore you can’t detect when the line gets free (the modem keeps it occupied, remember?
    also there is a schematic and everything else on the project page, for download

  5. I do not like being the downer on projects like this, but anyone building and using one should be very careful. Many locales have laws against recording a telephone conversation, even your own, if all parties are not notified. Some even forbid it completely, and count it as wiretapping.

    That said, I love the simplicity of this. It could be simpler, but it is a nice and understandable hack. Kudos to [Trax]

  6. Oh wait. The ‘RJ-11′(?) connector is the line in from the phone. The USB connection to the PIC is via USB to RS232 is only to signal the PC to record the reduced (from 15V-50V to a sound card friendly voltage) analogue signal from the third cord.

    Quite a cool little project.

    I would have used an old MP3 player (with recording capablities), and control it via a PIC in a similar manner. That means the device can be stand alone or connected to the PC via USB when needed.

  7. Check your state laws, not all states are 1 party states. 1 party states only require 1 person (usually 1 doing recording) to know about recording. 2 party states require that if some ones phone conversation is being recorded that both parties know about it. It can be a criminal offense.

  8. that’s correct. with an old mp3 player you wouldn’t need the PL-2303 usb-serial chip. it is pretty easy to “push” those buttons on a mp3 player with a PIC. now that version would be really mobile :)

  9. That could be another project. A phone recorder that automatically alerts people calling that their conversation is being recorder. Personally I hate phones and wouldn’t shed a tear if people stopped calling me because they didn’t want to be recorded!

  10. @Ali Raheem – “Information isn’t carried over the USB connection, that simply tells the computer to start recording from the audio out connector.”

    That sure sounds like information to me :-) I’m guessing you meant no audio is carried over the USB connection?

  11. wow – such put downs on phone lines…has no one seen the Matrix, hard lines rock ass…plus I love all the ‘experts’ that crawl out of the woodwork when it comes to doing something illegal (once burnt and all that).

    The 2P rule is easy fixed. When an incoming call is detected set pre-recorded mp3 in ready to play state, when the receiver pickup is detected play mp3 with “this call is being recorded” caveat and proceed with call.

    my work here is done :P

  12. So many people moaning about this and hardlines. There is a reason this has been made; it caters to the user. *nic phones are easy to record with abit of knowledge or just reading the manual. So writing about that would just be pointless. In fact for my work phone all i have to do is push a button and the server records it, lame encodes it and emails it to me…all out of the box

  13. this is part of the circuit…

    the complete hardware and software description is in the main site…

    you got to download it from there at the end of the article there’s a red button for download…


  14. James bond? Paranoid? How about every person in the western world, who all at least one time got shafted by promises by customer service over a phone that they would correct/do something and then found it was just forgotten/ignored, sometimes leading to large bills and disconnection from various services and legal issues.

  15. Landlines (pots) may be going away, but I can count on one hand how many times I ever picked up a handset and failed to get a dialtone. Compare that to how many times cellular services fail to complete or drop a call.

  16. Regarding the off-hook usb circuit and code that is constantly polling the status, you could also use the pinchanged event on one of the status pins of a common serial port… I use the ring indictator for simpile input monitoring quite frequently – works great and doesn’t require usb overhead or a program polling loop.

  17. @Agent420 – At the same time I am using USB to power the circuit (5V). And laptops don’t have serial ports any more… I could have used the LPT but they also are missing from laptops…
    This could have been done much simpler by using the V-USB library and a small ATtiny…

  18. Point taken. Though I have incorporated usb serial converter boards right into some projects, so I get both worlds.

    Nonetheless, good project.

    It would be interesting to look into making this standalone using one of those voice recorder chips.

  19. I haven’t scoured the ‘net, but the voice recorder chips I’ve seen only have a maximum capacity of a few seconds to a few minutes at best. Kinda useless to record an actual telephone conversation, or do you have no women in your family? ;)

  20. This item is a joke. I was making automatic telephone recorders for detective agencies way back in the 70’s and 80’s, over 40 years ago. The size of my unit was 1″ X 0.5″ X 0.25″ which is way, way smaller than that contraption shown above. Furthermore it did not require any power supply or batteries to function. It simply connected between the phone line and cassette recorder.

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