The present invention relates to a building security system for controlling building entry doors, establishing and controlling resident-visitor communication, interfacing visitor communication with ordinary telephone communication and establishing various other types of communications, monitoring and control functions. 
A common type of apartment intercom and door opening system known as an auto-dialer system utilizes only an intercom panel with a keypad at the building entrance door.  The panel is coupled to a dedicated telephone line leading to a central office exchange.  Communication is effected through the central office exchange between a visitor and a subscriber.  Although relatively simple to install, the auto-dialer system has a number of disadvantages.  First, it requires an extra line to the central office, the cost for which can be significant.  Second, when a subscriber line is busy a visitor at the building entrance door must simply wait unless the subscriber happens to have a call waiting system.  Similarly, when on a call to the intercom panel, an incoming call gets a busy signal unless the subscriber happens to have a call waiting system.  Finally, the auto-dialer system is not very secure as an unauthorized entry can be effected simply by using a remote dialer to dial the predetermined digit which opens the door. 
An early type of apartment-intercom and door release system which overcomes most of the previous problems is described in Canadian Pat.  No.  918,830 issued Jan. 9, 1973 which is a re-issue of Canadian Pat.  No.  806,751 issued Feb. 18, 1969 to John T. Matthews and also U.S. Pat.  No.  3,484,561 issued to the same invention for the same subject matter as the former Canadian Patent.  The Matthews system utilizes line switching relays to switch tip and ring lines running from a central office exchange to a subscriber apartment.  Operation of a line relay inserts a section of system tip and ring lines intermediate the central office lines and the subscriber lines.  Common switching equipment interfaces visitor calls at an intercom panel with subscriber apartment for each subscriber apartment in a building.  More particularly, the common switching equipment thus introduced in series with the tip and ring lines, allows the visitor to call the subscriber and the subscriber either to converse with the visitor or, if the subscriber is busy with an exchange caller to "beep" the subscriber and allow him to place the exchange called on hold and then transfer to the visitor.  By dialing preselected numbers the subscriber could either admit or deny access through the door and then return to his exchange call by simply operating the telephone dial.  The common switching equipment performs ringing, call-waiting, and ring-back signals.  Moreover, no wiring other than the apartment telephone lines and the lines to the entrance door are necessary. 
Subsequent to Matthews there were advances made in the implementation of such systems including the use of microprocessors to replace analog methods, the use of touch tone keyboards at the door panel and touch tone calling devices.  However, the Matthews type system has really been limited to functioning only as an apartment intercom and door release system. 
Building security not only involves authorized door entry but also includes such things as a provision for rapid access to emergency numbers, a means for allowing entry on a individual basis for selected individuals, a means for monitoring and recording entries and a simple means for allowing authorized persons to reprogram the panel in the event changes take place. 
Accordingly, it is an object of the invention to provide an improved building security system. 
It is a further object of the invention to provide a building security system which permits entry to selective individuals and provides a means for allowing authorized persons to reprogram he system, to deny access to any of these individuals or to permit access to yet other selected individuals. 
It is yet another object of the invention to provide a capability for rapidly dialing a predetermined number of emergency numbers on a dedicated line to a central office exchange. 
It is yet another object of the invention to provide a means for remotely programming the system. 
Finally, it is an object of the invention to provide an expansion port for additional control features such as a video controller, an elevator controller, an additional door controller and a printer for recording entries into the building.