1. Field of the Invention
The present invention relates to a communication system including an exchange and a plurality of extension terminals accommodated in the exchange, and particularly to an extension call processing technique in a communication system in which a plurality of extension terminals are connected to an exchange in a point-multipoint connection mode.
2. Description of Related Art
A communication system including a private branch exchange and a plurality of extension terminals accommodated in the private branch exchange has become widely popular in working places, etc. Further, recent propagation of ISDN (INTEGRATED SERVICES DIGITAL NETWORK) has also promoted the development and propagation of ISDN extension terminals which can connect to a private branch exchange in a point-multipoint connection mode by using ISDN as an extension terminal.
a conventional communication system, a service class management of extension terminals is performed by conducting call processing in accordance with class information which is predetermined every accommodation position of the extension terminal. The service class management means the management of functions which can be performed by extension terminals, such as connection control to a public line and control of other services. Further, the service class information means information required to perform service class management such as business/guest room class, interrupt class, etc.
When plural ISDN extension terminals are connected to a private branch exchange in the point-multipoint connection mode in the conventional communication system as described above, all of these ISDN extension terminals are class-managed on the basis of the same service class information because they have the same accommodation position.
Therefore, there occurs a problem that the service class management which is different for every terminal cannot be performed on the plural ISDN extension terminals which are connected to the exchange in the point-multipoint connection mode.
The present invention has been implemented in view of the foregoing situation, and has an object to perform the service class management for every extension terminal even when plural extension terminals are connected to an exchange in the point-multipoint connection mode.
In order to attain the above object, according to a first aspect of the present invention, a communication system comprising an exchange and a plurality of extension terminals accommodated in the exchange, is characterized in that each of the extension terminals includes means for transmitting call-initiation information while identification information is contained in the call-initiation information when a call is initiated, and the exchange includes memory means for storing a table representing corresponding relationship between the identification information of the extension terminal and service class information, and call processing means for searching from the table the service class information corresponding to the identification information contained in the call-initiation information when the call-initiation information concerned is received from the extension terminal, and performing call processing in accordance with the service class information thus searched.
Further, according to a second aspect of the present invention, a communication system comprising an exchange and a plurality of extension terminals accommodated in the exchange, is characterized in that at least one of the plural extension terminals includes means for transmitting call-initiation information while identification information is contained in the call-initiation information when a call is initiated, and the exchange includes memory means for storing a table representing corresponding relationship between the identification information of the extension terminal and the service class information, and call processing means for judging whether the identification information is contained in the call-initiation information when receiving the call-initiation information from the extension terminal, and searching the service class information corresponding to the identification information concerned from the table to perform the call processing on the basis of the searched service class information when the identification information concerned is contained in the call-initiation information, or performing the call processing on the basis of predetermined service class information in accordance with an accommodation position at which the call-initiation information is received when no identification information is contained in the call-initiation information.
In the present invention, when identification information is contained in call-initiation information transmitted from an extension terminal, the service class information corresponding to the identification information concerned is searched from the table, and the call processing is carried out on the basis of the service class information thus searched. Accordingly, even when plural extension terminals are connected to the exchange in the point-multipoint connection mode, the service class management can be performed for every extension terminal.