Some telephones, depending on the brand and model, have the intercom function, which allows to begin communication by sending the signal. When the signal comes, the telephone set rings a signal different from the standard ring tone call. After that the telephone temporarily switches off from the telephone line and works as an intercom.
Global Direct Telecom connects incumbent and mobile operators in Africa, the Asia/Pacific, the Middle East and Latin America to the major telecommunications hubs of North America and Europe.