Find all your DIY electronics in the MakerShed. 3D Printing, Kits, Arduino, Raspberry Pi, Books & more!


Aparently there’s a U.S. Special Information Tone signal for a dead phone line, and robot callers (telemarketers, debt collectors, etc.) listen for it, then remove the “dead lines” from their lists. Record it at the beginning of your answering machine messages to make (some) robots stop calling you! [via] Link.

(Photo by Flickr user scriptingnews)

Becky Stern

Becky Stern is head of wearable electronics at Adafruit Industries. Her personal site:



  1. james says:

    is that a standard headset adapted to the mini plug a phone uses? anyone got a link for that?

  2. Becky Stern says:

    follow the photo credit link for more information.

  3. Ryan says:

    Um, or just submit your phone number to If you get a telemarketing call you get after that you can get them heavily fined, so they don’t.

    I signed up years ago and haven’t gotten a single telemarketing call since.

  4. the steven says:

    I seem to remember buying a device, I believe it was called a “phone zapper”. I plugged it in and havent gotten a telemarketer call since.

  5. Sporkinum says:

    Does that still work? I bought a device to do that about 10 years ago. It runs off the phone line voltage.

  6. John says:

    Thinkgeek Retro Phone Handset

    Theres the link to that handset attached to the phone. Its sweet.

    I got a spy remote from the same site that lets me control the tv at the local bar. They wonder how the tv ends up on Comedy Central every time I’m there.

  7. tyler durden says:

    This may be especially useful in an election year!

  8. MadScott says:

    The “Phone Zapper” and similar devices simply respond to calls with the dead-line tone. The unintended consequence of putting this on your answering machine is that people you actually want to talk to may think your line’s out of order and hang up.

  9. James says:

    @MadScott: Your friends and family will only hang up if they don’t wait long enough to hear you say “Hello” or your outgoing answering machine message.

  10. Phone User says:

    Some high schools have an automated phone system that calls parents when their student is absent. Playing hooky just got easier.