A telephone service available both in digital and analogue systems allows displaying a number of the calling subscriber on the display. And where it is
possible the caller’s name can be also lighted up.
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.