Friday, May 20, 2011

Getting Rid of Unwanted Calls, Once and for All

If you’re like me, the first thing you did when you signed up with the phone company was to head over to, and entered your phone number into the national don’t-bother-me registry.

That will take care of most telemarkerters, except:
1. Charities, of which there seem to be no end.
2. Businesses with whom you are already a client.
3. Political calls.
4. Telemarketers who simply ignore the list.

So it’s sort of addressed the problem, but you still get unwanted calls.

One solution is to get a call zapper. This is a little black box you insert into your phone line. It’s supposed to send some kind of operator-signal when a telemarketer calls that will make the telemarketer think that your phone number is disconnected.

Cool, eh? Well if you have an answering machine or voicemail service, I can tell you how to do the same thing—absolutely free.

Special Information Tones

Have you ever dialed a number that was disconnected and heard three beeps, the first one low, the next one high, and the last one higher? That’s called a Special Information Tone (SIT). SIT tones were created because automated dialing equipment like modems, and network call detector/classifiers simply cannot decipher between a live answer or a recording, or what is said in a recorded announcement.

There are eight SIT tones in all. It turns out that one of them means “Number changed or disconnected.”

So how do you use this? Simple, really. You make an answering machine message that has this particular SIT tone at the beginning, then record your regular message.

When you get a call, you check your caller ID. If it says “private name, private number”, then you let your answering machine get it. The answering machine plays “beep beeeep BEEEP I’m sorry, I’m not available to take your call right now. Please leave a message after the tone.”

With me so far?

Let me tell you, this works. Right after I set up my answering machine I got an automated call from the Salt Lake County library that one of the books I had on hold was available. The computer never left a message—it just hung up. When I went to pick up my book, the system told me that the number it had on file was invalid and I needed to file a new number. (It still let me check out my book, though).


Since then I’ve gotten several political calls and charities. I just let the answering machine get it.

Setting it all up.

So, you can get ahold of a recording of a SIT tone. Go to Wikipedia and look up “Special information tones”. That will take you to the page you want. Next, scroll down to the list of example SIT recordings. The one you want is called “Intercept”, about half-way down the list. If you press the play button you can hear it.

Download the file and save it on your computer.

Next, you’ll need a sound editor. There are a number of good ones on the web. The one I like best is called GoldWave. You'll ned one that will allow you to splice two sounds together. It should also be able to play .ogg files.

Load up the SIT tone in your sound editor. Make a second recording of whatever greeting message you want. “You have reached the Abbott residence, but we are unable to get to the phone right now. Please leave your name and number after the meeep.”

When you splice the two sounds together, you’ll want about a half-second gap of silence, so people can hear your recording better. You’ll also want to adjust the volume of your recording so it is about as loud as the SIT tones.

You do not want to have the SIT tones loud and have your voice soft, or your friends will think your phone got disconnected! Play with the volume on your voice recording until it is about as loud as the SIT recording.

When you’re ready, you’ll have to move your answering machine close to your computer speaker—I mean really close, or the recording won’t be loud enough. You’ll want to play back the recording from your answering machine until it sounds loud enough that you can hear it completely.

That’s really all there is to it.


You might want to warn your friends and family, just to be on the safe side. When people call you and the answering machine gets it, there will be a moment of confusion when they hear the error tones.

You might miss important messages that way, like when the library calls you about that overdue book, or the bank wanting to tell you that someone has swiped your credit card number and wants to buy a new 60” TV.

There are no perfect solutions to the telemarketer conundrum. This technique works, but there are downsides. Use this knowledge at your own discretion.

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