Is a telephony service allowing the distribution of telephone calls from one telephone number in the group consisting from several telephone lines, using the special algorithm, which determines the line receiving a call.
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.