Apartment entry morse-code lock

[Bozar88] lives in an apartment building that has a buzzer at the front security door. Guests find your name on the panel next to that door, and press a button to ring the phone just inside the entry of each apartment unit. He decided to extend the built-in capabilities by adding a morse-code entry password which unlocks the security entrance automatically (translated).

He designed a circuit and etched his own board which fits nicely inside of the wall-mounted phone. It uses an ATtiny2313 to implement the coding functions. The device attaches to the intercom line in order to detect incoming button presses from the entry panel. There’s some protection here to keep the signal at or below 5V. The output is two-fold. The microcontroller can drive the microphone line using a transistor, which gives the user audio feedback when the code is entered. To unlock the door an opt-isolated triac (all in one package) makes the connection to actuate the electronic strike on the entry door.

The video after the break is not in English, but it’s still quite easy to understand what is being demonstrated.

[Thanks RicoElectrico]

Comments

  1. DanJ says:

    Clever use of an existing installation.

    • No One says:

      Agreed. I think this is the most interesting hack I’ve seen in quite some time.

      I wish it would use an adaptive algorithm for the morse input instead of assuming you’re doing 0-0.3s and 1s inputs.

      • n0lkk says:

        Morse Code is a skill set. The security of this system depends on the owner knowing the Morse code, knowing the actual pass word/phrase, and the ability to send Morse somewhat precisely. While others may have the skill, they may not know the password. Using an adaptive algorithm, could allow anyone who has heard the password often “get lucky” and gain access. Of course there could be those who over hear it once, and has the skill may just walk right in. Convenient security isn’t really security.

  2. tehkillerbee says:

    I have actually been working on a similar project, but where the intercom is used as a one way modem.

    Neat idea anyways, I will try to implement this aswell :)

  3. tehkillerbee says:

    I have actually been working on a similar project, but in my case the intercom is used as a two way data connection, like a modem.

  4. fartface says:

    Uber Clever! This is the kind of hack I expect from HAD!

  5. Patrick says:

    does it also have a learning mode, so you can switch morse sequence.

    Just as “Secret Knock Detecting Lock”??

  6. Italo says:

    Can anyone point me to the protocol used in this kind of analog intercom system?

  7. my2c says:

    - On a similar note, I dropped a pay as you go cell phone into the wall in an apartment behind the intercom box that had some basic hardware to detect a ring, and close a relay which would trip the entry door to unlock. Another handy ‘keyless’ entry, give the phone number a call to let yourself in.

  8. Ivan says:

    Just make sure you pick a hard code and change it periodically… I’d hate to be the one that let the thieves in.

    Nice and very clever idea! :)

  9. Hirudinea says:

    This is such a simple, clever idea I don’t know why it isn’t standard in all apartment intercoms.

  10. Pun says:

    Pure genius. Perfect use of an existing system, and a very clean implementation. :)

  11. CubedOptimism says:

    One thing he could do to cut down on the risk of eavesdroppers learning his code is to make the buzzer stop sounding after part of the code has been transmitted. That way the complete code wouldn’t be sounding audibly.

  12. Marcin Rybak says:

    the only problem is that when one of your neightbours would get an information that you have such nice thing, you’re going to be his butler :)

  13. lupin003 says:

    Nice idea. But this only helps entering the front door. If you forgot your keys you could just as well ring one of the neighbours. But either way you’d have a problem opening your flat door unless you also modify that with an automated opening system (which sure would prove to be a bit more complicated).

    Another problem is that you have to remove it when you move out of your flat.

  14. ErikH says:

    Nice! Got one myself – even used the AT2313 :) Build it around 5 yours ago to gain access to my appartment complex. No audio feedback and it only switches on if the first pulse is a short one and will suppress the door bell. A long pulse will result in normal operation, so no one will notice it’s there.

    A keypad will eventually gain me access to my apartment, so no more worries about leaving my keys inside ;)

  15. andsetinn says:

    Brilliant idea although the security is not like in Fort Knox. But then again, large crowbar can usually overcome most security measures.
    I also like My2c version and CubedOptimisms idea for improvement.
    The next version would be to use pattern recognition. Let your doorbell disconnect all others for a second or two. Then use the buttons for you and your neighbors as sort of combination code. :)

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