telescum tape label

[screaming operator logo 46K]

Telemarketing "Zapper" Device

and Other Electronic Anti-Telemarketing Devices

This page describes:

The TeleZapper
and alternative techniques
Answering Machine with Caller ID Intercept
(unfortunately only the Casio TA-140/145, out of production)
Mailboxing Telephone Answering Machines
the Nortel Meridian M-9516, fortunately back in production

Computer Version of Mailboxing Telephone Answering Machines
Automatic Fax/Telephone Feature on Certain Fax Machines
Telco "Call Intercept" Service
or "Telemarketer Call Blocking"
the TeleCrapper
An automatic unattended verbal response program

This page was originally written to describe the Zapper device but I've also included other devices, such as the mailboxing telephone answering machines.

Some of these devices use caller ID and SIT tones, which work with the North American telephone system and other systems conforming to the North American standards.


TeleZapper is a device which emits a SIT tone which tells the telescum's "call progress detection" equipment that they have a disconnected number. This results in a disconnect from anyone using automated equipment. After approximately 3 attempts from each of the major telemarketing operations, your number is removed from their master lists.

$30 at Radio Shack and other outlets. Also at where they have a $30 and a $50 model that appear to do the same thing.

Does it Work?

Yes. While predictive dialers can be programmed to ignore the Zapper but that takes away their ability to automatically delete bad numbers.

The Zapper will not work with an external "voice messaging" service. It requires a real, live answering machine. So spend the extra bucks and get a real answerin' machine. NOTE: Get a digital answering machine. Telescum are starting to record messages. Digital machines have a "delete" button.

It will also work for households in which most calls are answered.

How it Works

It is possible to confuse predictive dialer software with a false SIT tone. The Zapper generates SIT tones which tell the predictive dialing software that yours is a non-working number.

The device senses when a phone goes off-hook (voltage drop), presumably after a ring (50 volts), and emits a SIT tone. Then the answering machine or live human answers the phone. The manufacturer recommends a 2 second delay but that's just to allow the completion of the SIT tones. You can talk immediately after the SIT tones.

As I indicated, it won't work for external "voice mail". This is because with external voice mail, the phone never goes "off hook".


  1. makes annoying noise (the SIT tones) whenever active
  2. requires delay in answering machine message
  3. is not effective when used with "voicemail" services
  4. cost ($40)

Alternative Technique

Some of these are also mentioned above.

The SIT tones can be inserted into the answering machine message itself.

The following is a .wav file for an invalid number SIT tone: errorbeeps1.wav (15k), from If it doesn't play clearly directly from the net, try downloading it. Here's a digitally synthesized (45k) sample.

An "Intercept SIT tone" is what you initially hear when you reach a North American number which is out of service or otherwise invalid.

Anecdotal reports are that the first beep controls predictive dialer response. This contradicts Dialogic's literature, and so I recommend this only if you don't want the three tones.

Answering Machine with Caller ID Intercept

Caller ID Intercept or Caller ID Screening is the ability to control the answering machine according to the caller ID output. In North America, telescum calls generally carry the caller  indication, "unavailable" or "out-of-area".
(This indication is shared with most T-1 lines and some phonecards, and simply indicates that the caller's equipment doesn't provide the caller ID channel.)

It is important that the caller ID intercept be able to direct specified callers to an answering machine. Fortunately, this seems to be a characteristic of both devices on the market.

Casio Phonemate TA-140

The Casio Phonemate TA-140/TA-145 has been discontinued, and as of 5-03 could not be found on eBay. Fortunately, the Nortel 9516CW, described below and the Radio Shack mailboxing answering machine are now available at similar prices.

The Casio (Casio Phonemate) TA-140 (or TA-145 if you want a translucent blue case; $40. for either) has an option to direct "unavalable" calls to the answering machine message. Most telescum calls in North America must display caller ID, so using the "unavailable" signal to distinguish telescum calls no longer works.


  1. Obsolete due to use of caller ID by telescum, at least in North America.

Mailboxing Telephone Answering Machine

These are the Nortel Meridian M-9516 12 Box Caller ID Phone (sometimes labeled Sprint), and Radio Shack TAD 3816 speakerphone.

update: Similar units are now being sold by Radio Shack, both with the speakerphone like the original Nortel model, and in an answering machine-only version. The RS branded phones are not Nortel phones, but do have the mailboxing function.

The M-9516 12 Box Caller ID Phone is able to sort calls by caller ID classification. The original Nortel device has 12 mailboxes, so particular groups of callers can get their own boxes, and presumably the owner can selectively review messages from the different mailboxes when calling remotely. The significant aspect of this is that "unavailable" calls get dumped into their own mailbox. "Unavailable" are usually T-1 lines, and most telemarketers come in that way. The different mailboxes can have different messages.

With a caller ID mailboxing answering machine you can use a normal (or adnormal) outgoing message for most calls. Then you can use a message intended to hang the answering machine detection for just the "Out of Area." calls. (Remember "unavailable" may be legitimate business calls too.)

The newer Nortel Meridian M-9516CW 9 Box Caller ID Phone has caller ID on call waiting capabilities. If you may get call waiting in the future, get this one, or the Radio Shack device:

Brand: RadioShack
Catalog #: 43-3816
cost $60.00

The RS phones are different from the Nortel units, but RS's text form product manuals still identify "Nortel 9516". The Radio Shack phones don't take daughter units and they're not multiline phones.

RS also has the same thing as an answering machine without the speakerphone, for about $10 less, but I recommend the one with the speakerphone.

Mailboxing phones still are very useful for particular persistant callers. Once identified by caller ID, these calls can be channelled to SIT tones or whatever message desired.

the Radio Shack product manuals
9516.html more descriptions of the "Nortel 9516"

The following links may be inactive:

Wally's World
description of NORTEL Meridian M-9516 12 Box Caller ID Phone from Wally's World


  1. includes digital answering machine for deleting any recorded messages that get through
  2. has versitility
  3. caller ID function
  4. can be used to divert calls "targeting" your number.
  5. speakerphone (except the answering machine-only version)
  6. it's fun.


  1. Ability to flag calls with Caller ID "unavailable" is obsolete due to use of caller ID by telescum, at least in North America. (Fortunately, this also means that the mailboxing phone is unlikely to interfere with overseas calls and special collect calls such as prison calls.)
  2. The original M-9516 may be out of production (but is still available, mostly rebuilt units)
  3. Cost of caller ID service. Typical charges are $90.00/year.
  4. Outgoing messages on the Radio Shack unit are limited to 30 seconds.
  5. The Radio Shack unit won't separately assign mailboxes as "announce only". It's either all announce only or all announce-and-record.

"Punchthrough" Answering Machines

All calls are answered by an answering machine, but callers who know the "secret code" (and have a touch tone phone) get through. In the anti-telescum format, the code is verbally stated on the answering message.

e.g., "To speak with the Schmuck family, please dial 123."

The "punchthrough" feature is found on various answering machines, and is a standard feature of most fax machines and some computer answering machine programs.

There's a different "punchthough" function which permits callers to interrupt the message before it's complete. Most tone operated machines have this second "punchthough" feature.

Telescum use predictive dialers and therefore generally do not hear the code. (Telescum using war dialing systems and recorders to generate leads for manual dialing are blocked at the automated call.)


  1. easy to configure
  2. caller ID not required
  3. allows frequent callers to bypass answering machine message
  4. augments some other call filtering systems by permitting callers to bypass the message.
  5. fake telemarketing calls are obvious because the caller will generally "punch through".


  1. requires all callers to go through sequence (at least during telescum hours)
  2. requires touchtone to bypass the message.
  3. may interfere with some collect calls (most of US), depending on how they display on caller ID.

Computer Version of Mailboxing Telephone Answering Machine

This is an answering machine program which works through the computer's modem. Since most modems are Caller ID capable, the program is able to provide the caller ID "mailboxing" function, with discrete messages. - Advanced Call Center software. I think it's $40.00

The website lists the "AT" commands and instructions to verify whether your modem has caller ID capability. If you can load a terminal program (Telix, Hyperterm, etc.) you can test these. Otherwise use their demo. (Your modem's caller ID function does not give you caller ID. That's enabled by your dialtone provider.)


  1. runs from your computer
  2. can delete any recorded messages that get through
  3. caller ID function
  4. is probably a speakerphone


  1. runs from your computer
  2. may interfere with computer programs which are intolerant of multitasking, such as CD burning.
  3. I have no idea if it can hand off incoming faxes.
  4. May interfere with prisoner collect calls (most of US), depending on how they display on caller ID.
  5. Windows only (If you're running Linux, here's your chance to get your name on some Open Source!)

Automatic Feature on Certain Fax Machines

This is sometimes called a "fax-telephone" feature.

Some fax machines (e.g., Brother 600/700 series) have a capability of automatic operation. If no fax "hailing signal" (beep tone) is received, the fax machine rings through its speaker (i.e., rings like a telephone) after it answers the phone. The caller hears a secondary ringback that sounds like a UK ring. The person called then picks up the phone and talks. Basically the fax machine is acting like an answering machine without the ability to transmit or receive a voice message.

The purpose is to allow someone who is expecting a fax call to receive an intervening voice call. This is useful for people with "on-request" fax machines in a home office, and people who wish to receive occasional voice calls on their fax line. Therefore, it's a common feature on home-use fax machines.

This is different connecting a TAD to the fax machine. This is different from "remote signaling" of the fax machine.

Because of the bahaviour of these "fax-telephone" machines, predictive dialers report the line as "out-of-order". Three attempts and you're number's been blacklisted! (I have not tested this against predictive dialers, so this assessment is based on technical knowledge only. Both the pause in the ringback and the UK-style ringback sound should generate "error" flags on predictive dialers.)

This use of the fax machine is practical if:

  1. You have one of these machines.
  2. You are conveniently able to use the feature by switching it on and off at the appropriate times. This makes sense if you routinely switch the fax machine on and off (or switch the answering machine on and off), but would be a major nuscience if you basically ignore the fax machine.
  3. You are willing to have the fax machine answer the phone when the feature is invoked. (It won't give callers its modem noise when it answers, but it will always answer the phone.)


  1. Is free if you already have the fax machine with this feature
  2. Doesn't require caller ID
  3. Is less intrusive than SIT tones.
  4. Can be selectively operated, e.g. during peak telescum hours.
  5. Can be selectively operated during dinner hours when you are home.
  6. Detects fraudulently muted warning tones for recording devices, which are often used by telescum. (The fax machine's "eavesdropping modem" will respond to these muted tones by turning on.)
  7. Works with incoming calls from cell phones.


  1. Requires physical operation of the device when you wish to use it and when you wish to leave the house.
  2. Answers the phone before you are ready to talk, which results in additional charges for some callers.
  3. Answers the phone automatically whenever switched to the "fax/telephone" mode.
  4. You may not notice if fax machine is inadvertantly left in "wrong"mode.

Telco "Call Intercept" Service

(Telemarketer Blocking Services)


The details vary with dialtone providers, but in general, all calls coming in "blocked", "unavailable" or the equivalent get intercepted by automated equipment. The caller receives a recording announcing the intercept, and is requested to identify him/herself. After identification, the user (the called party) hears a distinctive ring while the caller is placed on hold.

If the user picks up, the user hears the identification, and chooses between "accept", "reject", or "reject with 'Add me to your Do Not Call list.'" The call is either placed or a message is given to the caller.

If the user doesn't respond, the caller is put through in approximately 20 seconds, which allows use of an answering machine.

A bypass code can be provided by the user to known callers to allow them to bypass the intercept. This is useful, should friends and family call from a T-1 line or calling card. (The "bypass code" for caller&ID blocked phones is "1182" before dialing the number!)


  1. Should block telescum calls.
  2. Will probably block most telescum messages to answering machine, since automated equipment won't accomodate the intercept.
  3. Makes harassment calls difficult.


  1. Cost: Typically $150.00/year, including caller ID.
  2. difficult to program answering machine to accept both regular calls and intercepted calls with the 20 second delay. (The M-9516 solves that problem.)
  3. Generally cannot be set to automatically accept caller&ID-blocked calls.
  4. Blocks automated collect calls. (If you need to accept prisoner calls (in most of the US), you can't use this.)

the TeleCrapper

Unfortunately, this is still in the "a bunch of junk RS parts" stage. But it seems a voicemodem TeleCrapper (or combination TeleCrapper - answering machine) is a short step away.

The TeleCrapper is an automated verbal script program which provides unattended responses to telemarketers. It responds to caller ID to load a stack of .wav files. It detects silence and uses the .wav files engage the telemarketer in conversation. Instructions available at (the TeleCrapper)

All of this is recorded and is a lot more amusing than listening to telemarketers on my phone try to talk to the recording of my dog.

The TeleCrapper website includes some sample recordings using two different stacks of .wav files.

Requires a caller ID-capable voice modem. (Most 33.6 and higher, but caller ID capability on modems is largely undocumented because it isn't generally used.)


  1. Establishes a completely new factor for telemarketers to deal with (or avoid) in their scripts and harassment strategies.
  2. Once bitten, a telemarketer operator will be more circumspect with future "sales" calls.
  3. Uses existing equipment. Turn your 386 into a the TeleCrapper server.
  4. Makes harassment calls difficult.
  5. Can work with separate answering machine.
  6. The program is free.
  7. Open source. Ordinary answering machine should be an easy add-on routine for any programmer.
  8. Can work with Telezapper or other "off-hook" detection device, but that device must be connected to modem's telephone output to block its activation.
  9. It's childish!


  1. A big one -- It's not yet implemented as a DOS or WinDoze plug-and-go program. It seems that the implementation would be a simple one, however.
  2. Requires that the telescum make one attempt prior to activation, because that caller ID string must first be identified.
  3. Cost: Caller ID typically $75.00/year. (if you don't already have it.)
  4. May be difficult to program. (or it may be easy!)
  5. May not incorporate answering machine function in program (but home answering machine will work).

More boring technical data - (this site)
9516.html more boring descriptions of the "Nortel 9516"
back to Counter-Telemarketing Tactics - (this site)
Defeating Answering Machine Detection

Courtesy of Stan Protigal

Comments about this site: email me
Feel free to link to this site.

site first posted November 3, 1996; this page 1999
rev. October 9, 2007. This page copyright 1999, Stan Protigal
This website can be found by searching for "The Telemarketing Scum Page" on a search engine.

SCN Home Page
Seattle Community Network
SCN Member Pages