Callback, also known as international callback , is a system for avoiding regular phone company long-distance charges by having a call initiated from within the United States with the originating caller joining in a conference call. Here's how the procedure works:

• A call originator (for example, someone in South America) calls a predesignated number in the United States, waits until it rings once, and then hangs up.
• A machine in the office where the phone rang recognizes that the phone number was called and knows the phone number of the party that called it (because it was the only party that knew the number).
• The machine places a call (which may be a local or a long-distance call) that originates from the U.S. location and also calls the party who initiated this procedure, thus arranging a conference call but at the U.S. long-distance rate.
• In another variation, the automatically-generated call from the U.S. may call the originator and ask the originator to dial their desired number or provide a U.S. dial tone.
• The originator (who subscribes to this callback service) is billed by the U.S.-based service at its own rates.

In localities where portable phone (cell phone) companies do not charge for incoming calls, callback is also sometimes used to avoid airtime charges for outgoing calls.

22 Mar 2011