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.
Companytel is a italian company created in Rome , specialized in the development and production of telecommunications equipment. It is comprised of specialists in the design and production of data and voice transmission equipment.