| 摘要 |
PURPOSE: A method for discriminating a subscriber number not used in an exchange is provided to retrieve a database recording whether subscriber numbers are used. CONSTITUTION: An exchange records using states of subscriber numbers assigned within the same line during a determined test period, on a flag bit of a database(ST21-ST23). If the database is constructed, the exchange sets up a test time retrieving the database in order to discriminate a subscriber number not used(ST24). If a specific subscriber number is currently used, the exchange registers the specific subscriber number as a using subscriber number(ST25-ST27). If the specific subscriber number is currently not used, the exchange registers the specific subscriber number as a subscriber number not used for a long time, and outputs the subscriber number not used for a long time(ST28-ST29).
|
