Private branch exchange capable of adding a calling station ID number to the call signal

A private branch exchange to transmit a SETUP message to an ISDN, comprising:

• memory means for storing respective direct inward dialing numbers of a plurality of extension terminals:
• detecting means for detecting a calling request to the ISDN from one of the plurality of extension terminals;
• identifying means for identifying the direct inward dialing number of the one of the plurality of extension terminals based on the direct inward dialing numbers stored in said memory means, the direct inward dialing number of one of the plurality of extension terminals being a number for directly connecting an incoming call to the exchange with one of the plurality of extension terminals when a terminal connected to the ISDN makes an outgoing call to the ISDN using the direct inward dialing number;
• and
• setting means for setting the SETUP message by using the direct inward dialing number of one of the plurality of extension terminals identified by said identifying means as a calling party information element.

A private branch exchange for exchanging a plurality of extension terminals, comprising:

• memory means for storing a plurality of direct inward dialing numbers corresponding to the plurality of extension terminals, the direct inward dialing numbers being numbers for directly connecting an incoming call to the exchange with a corresponding one of the plurality of extension terminals when a terminal connected to an external network makes an outgoing call to the external network using one of the direct inward dialing numbers;
• detecting means for detecting a connection request to an external line sent by one of the plurality of extension terminals;
• selecting means for selecting one of the plurality of direct inward dialing numbers corresponding to one of the plurality of the extension terminals;
• and
• transmitting means for transmitting the one of the direct inward dialing numbers selected by said selecting means to the external network.

A private branch exchange for exchanging a plurality of extension terminals and transmitting an SETUP message to an ISDN, comprising:

• memory means for storing a plurality of direct inward dialing numbers corresponding to the plurality of extension terminals, the direct inward dialing numbers being numbers for directly connecting an incoming call to the exchange with a corresponding one of the plurality of extension terminals when a terminal connected to the ISDN makes an outgoing call to the ISDN using one of the direct inward dialing numbers;
• detecting means for detecting a calling request to the ISDN sent by one of the plurality of extension terminals;
• selecting means for selecting one of the plurality of direct inward dialing numbers corresponding to the one of the plurality of extension terminals detected by said detecting means;
• and
• setting means for setting the SETUP message by using the direct inward dialing number selected by said selecting means as a calling party information element.

A private branch exchange for exchanging a plurality of extension terminals, comprising:

• memory means for storing a direct inward dialing number;
• determining means for determining whether the direct inward dialing number corresponding to a calling extension terminal is stored in said memory means;
• and
• transmitting means for transmitting a selected one of (1) the direct inward dialing number corresponding to a specific one of the plurality extension terminals and (2) a number corresponding to the plurality of extension terminals based on a determination by said determining means, to an external network,
• wherein the direct inward dialing number is a number for directly connecting an incoming call to the exchange with the specific one of the plurality of extension terminals when a terminal connected to the external network makes an outgoing call to the external network using the direct inward dialing number, and
• the number corresponding to the plurality of extension terminals is a number for connecting a non-specific one of the plurality of extension terminals when the terminal connected to the external network makes the outgoing call to the external network using the number corresponding to the plurality of extension terminals.

A private branch exchange for exchanging a plurality of extension terminals and transmitting a SETUP message to an ISDN, comprising:

• memory means for storing a direct inward dialing number;
• determining means for determining whether the direct inward dialing number corresponding to a calling extension terminal is stored in said memory means;
• and
• setting means for setting the SETUP message by using a selected one of (1) the direct inward dialing number corresponding to a specific one of the plurality of extension terminals and (2) a number corresponding to the plurality of extension terminals, based on a determination by said determination means,
• wherein the direct inward dialing number is number for directly connecting an incoming call to the exchange with the specific one of the plurality of extension terminals when a terminal connected to the ISDN makes an outgoing call to the ISDN using the direct inward dialing number, and
• the number corresponding to the plurality of extension terminals is a number for connecting a non-specific one of the plurality of extension terminals when the terminal connected to the ISDN makes the outgoing call to the ISDN using the number corresponding to the plurality of extension terminals.