| 摘要 |
PURPOSE: A method of servicing a caller ID by using a hierarchical structure is provided to divide a CID(Caller ID) service into switching system, module and port, and three layers, and to automate CID management, thereby efficiently managing line facilities at low cost. CONSTITUTION: A telephone number exchange confirms whether a service is able to be supplied when a CID service is requested from a line, and if entire modules including the line are capable or a present module is capable, the exchange opens a CID line(S401-S405). If the present module does not support the CID service, the exchange confirms whether a usable port is in the module, and if so, a corresponding subscriber selects a new exchange port for the CID service(S406-S408). If an outside line of the new port is the same line, the exchange port performs an inside line operation to have a CID service line, and if the outside line is an optical line, the exchange port simultaneously has the outside line and an inside line to have a CID service line(S409-S414). If usable ports do not exist in all modules and all subscribers occupy the ports, user ports requiring the CID service are crossed with user ports not-requiring the CID service(S415-S425).
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