A Toll-Free Number is a special telephone number which is free for the calling party, and instead the telephone carrier charges the called party for the cost of the call. A toll-free number is identified by a service access code, from a dialing prefix range similar to a geographic area code. The specific service access numbers can vary by country.
The capabilities of toll-free services have evolved as telephone networks have moved from electro-mechanical call switching to fully computerized stored program controlled networks.
For example, in today's computerized networks, use of a toll-free number often allows for capture of telephone numbers of incoming calls. In the United States, for example, toll free numbers usually capture the telephone number of the caller through automatic number identification, which is independent of caller ID data and captures caller information even if caller ID is blocked.