Abstract: An integrated telephone, intercom, security and control system for a building having a plurality of units, utilizing a plurality of telephone lines located throughout the building which are connected at one end to telecommunications equipment located in the units and throughout common areas of the building. A digital switching device is connected to the other end each of the telephone lines and arranged to connect at least one of the telephone lines to at least one of another of the telephone lines or to an outside telephone line at the option of a user of the telecommunications equipment. A plurality of sensors located in the units and throughout common areas of the building are arranged for generating signals in response to conditions therein, which are then transmitted to a plurality of control modules connected to the digital switching device by at least one of the telephone lines.