| 摘要 |
Techniques for analyzing interactions of call routing features in a telephone system and implementing the features. Analysis and implementation are based on the recognition that a customer intends a call routing feature to apply to a telephone number which represents either a subscriber to which a call should be routed or a telephone number to which a call should be routed. From this recognition flow two classes of routing features: telephone features, which apply to telephone numbers representing telephones, and subscriber features, which apply to telephone numbers representing subscribers. How a given feature interacts with other routing features depends upon which of of the two classes it belongs to. Routing features may be implemented by keeping track of a telephone number which functions as a subscriber pointer and of one which functions as a telephone pointer and recursively invoking functions for subscriber and telephone features. The recursive invocations permit forwarding chains of any length. The techniques have also led to the development of a number of new call forwarding and call blocking features.
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