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How Automatic Dialers Work

Automatic Dialer Technology

Each telemarketer at a call center needs his own telephone with a headset connected to a dedicated phone line for automatic dialers to work properly.
Each telemarketer at a call center needs his own telephone with a headset connected to a dedicated phone line for automatic dialers to work properly.
William Thomas Cain/Getty Images

A simple automatic dialing systems isn't very expensive or complicated to set up. You need four things to create a basic system:

  • A computer, preferably a desktop model
  • A voice modem
  • Auto-dialing software
  • An active telephone line

A voice modem allows a computer to play or record audio over a telephone line. On a standard desktop computer, there's room for two to four internal modem cards. Each internal modem can only be connected to one phone line. So the more modems you have, the more phone calls the computer can make simultaneously.


If the auto-dialing system is going to be used in a call center with multiple live operators, then each operator will need his own telephone with a headset connected to a dedicated phone line. Autodialers can work over both the regular public switched telephone network (PSTN) or Voice over IP (VoIP).

The most important part of the auto-dialing system is the software. The software tells the computer which numbers to dial and how to respond to different situations (if an answering machine picks up, a human answers, a busy signal, et cetera).

Voice detection is the technology that allows auto-dialing software to detect the difference between an answering machine and a human voice. Here's how voice detection works:

  1. If nobody picks up the phone for four rings or more, about 25 seconds, then there's an increased likelihood that the call will be answered by a machine.
  2. When the call is answered, the software measures the length of the first words spoken and waits for a pause. If the initial response is a short burst of words (one to three seconds) followed by a pause, then it's a human ("Dr. Johnson's office. How can I help you?")
  3. The software then passes the call to a live operator or plays a pre-recorded message.
  4. The telltale pause that accompanies most telemarketing calls is caused by the time it takes for the software to recognize a human voice and route the call to an available operator.

[source: Telecomlogic]

One of the most interesting developments in auto dialing software is predictive dialing. Predictive dialing is most useful in a call center setting, where multiple operators are making simultaneous calls. Predictive dialing technology uses a complicated algorithm to anticipate when an operator will be free to handle another call. Predictive dialing software analyzes several factors:

  • how many calls are answered by live people
  • how many calls are answered by machines
  • how many calls are never answered or encounter busy signals
  • the length of a typical call when answered by a live person

Using this information, the predictive dialing software can calculate exactly how often to start dialing a new number to maximize the amount of time the live operators are on the phone and talking. The system will often dial numbers when no operators are available, knowing that an operator is likely to end a call right when another one begins.

Interactive voice response (IVR) is an autodialing technology that supplies interactive menus on outgoing calls. For example, a marketing or demographics company can autodial consumers and present them with an interactive poll they can answer with their telephone keypad or voice responses.

Now let's look at some of the most common services and features associated with autodialers.