(Automatic Call Distributor) A computerized phone system that responds to the caller with a voice menu and connects the call to the appropriate agent. It can also distribute calls equally to agents. ACDs are the heart of call centers, or contact centers, which are widely used in the telephone sales and service departments of all organizations.

Computer telephony integration (CTI) has produced very sophisticated ACD systems. For example, a call center might want to handle 70% of all calls in 30 seconds or less, but if it can identify a high-value customer based on calling number, it may want to ensure the call is answered more quickly. In this "priority routing," the ACD must recognize the calling number via ANI or Caller ID, consult a database and then route the call accordingly.

Human or Machine
"First-party call control" uses a human to route the call after either speaking with the caller or analyzing the caller's history. "Third-party call control" routes the call automatically.

Many Options
Routing can be based on the caller entering an ID or account number into a voice response unit (see IVR). Another option is setting up unique telephone numbers; for example, one for sales and another for service, and routing the call based on the number dialed (see DNIS).

ACDs can also incorporate "skills-based routing," in which the caller is routed with appropriate data files to the agent who has the appropriate knowledge to handle the situation, such as speaking a different language.

Handling more than phone calls, some ACDs can also route e-mail, faxes, Web-initiated calls and callback requests.