No Telemarketers!


How I Beat Telemarketers

Update 3/21/04

At the same time I was developing my anti-telemarketer device below, a commercial version with almost the exact functionality was being introduced to market.    It is called the Sreen Machine.    I highly recommend it over the device I built.   It does the same thing for about $40.   I bought one after my Voice Pro quit working.    The Voice Pro just seems to have lost it's firmware.



I was disgusted with telemarketing calls interrupting whatever I might be doing at home, so I set out to devise a way to screen calls so my phone would only ring if the call was from a non-telemarketer.

I had gotten a Telezapper for Christmas. This simple device sounds a tone whenever you pick up a phone in your house. The tone tells the telemarketing auto dialers that the line is not in service. Eventually this "dead line" information is supposed to propagate to the big database of telemarketer phone numbers in the sky, and the volume of calls you get is supposed to decline. The problem with this device is that you are interrupted and must pick up the phone. It didnít solve my problem. I donít ever want to answer the phone form a telemarketer.

Note: You can make your own telezapper by recording the tones on the beginning of your answering machine message. It will play when it answers and get your number off some databases. Here are the tones in .wav format: SIT-VC.WAV

My device would be required to:

  • Answer the phone immediately without it ringing in the house.
  • Announce that I do not accept telemarketing calls.
  • Require the caller to press a number to dial through the house.
  • Ring the phone in the house.
  • Connect the incoming line to the phone when it is picked up.

Before I started designing, buying components, and soldering, I did some searching for a similar device. Apparently Radio Shack had a similar device at one time but discontinued it. My search led me to a Small Office - Home Office (SOHO) PBX. These boxes are designed to serve a small office where there might be a couple of incoming lines and a few extensions. They are packed with features like voicemail, intercom, call screening, Auto Attendant, hold & transfer, music on hold, etc. I quickly realized there were enough features in these things to easily configure my desired device. The downfall was the price. Typically $600 to $1200.

Good old Ebay led me to an outfit that bought the remaining SOHO PBX inventory of a company that went out of business.

I bought a unit for about $120, installed it, and configured it to provide only the functionality I wanted. Probably 1% of its functionality.    There is a Yahoo Group of users for this product where you can get more information.

So now when you call my house, the phone does not ring in the house. You immediately hear:

Don‪t hang up. This is not an answering machine.
This private residence does not accept telemarketers, or telephone solicitations of any kind. That includes solicitation for charities, free offers, and religion. To dial through to the house press zero at any time during this message. Telemarketers and solicitors dial 315 for further information. Telemarketers dialing 0 will be prosecuted in accordance with the Telephone Consumer‪s Protection Act of 1991

If you press 315 you hear:

Telemarketers must supply all the following information. Omission of each item of information constitutes a violation of the Telephone Consumerís Protection Act of 1991 and will result in a $500 fine for each violation. You must leave a message with the following information:

Name of the Telemarketing Company Calling:___________________________
Complete Address:________________________________________
Including City, State, Zip:_______________________________
Phone Number:___________________________________
ACTUAL Full Name of caller:_____________________
Name of the company or product you are Representing
The represented company's address:__________________
The represented company's phone no:_________________
The Date and Time of this call.
A statement that this number will be added to your do not call list.
In addition, you must mail a copy of your do not call list policy to
~my mailing address~

If you just hang up now you will be in violation of the afore mentioned act.

If you press zero, you are put on hold and you hear music while the phone is ringing in the house.

The SOHO PBX is installed in a closet near a convenient location to intercept the main phone line coming into my house, before it reaches any phone jacks.   It has one incoming line from the telco, and only one extension is used to feed all the phones in the house.   One limitation I have found is the PBX's limitation on ringer equivalents it can drive from its ring generator.    If too much power is drawn by too many phones connected, it will only ring once and then drop the call.   This can be overcome by turning off some ringers, or using one of the newer cordless phone systems that has multiple handsets.

The end result - no interruptions!


Don't forget to register for the National Do Not Call list at


  © Copyright 2003, Tom's Institute of Technology.



[Home] [No Telemarketers!] [Coffee Cup Engine] [Mill/Drill Conversion] [Pinball] [Pinball Mover] [Trike Tamer] [Engines] [Engines2] [Stepper Generator] [E-Bike]