| 摘要 |
This invention relates to a method and apparatus for establishing connections over a public switched telephone network to a customer whose telephone number is in a block associated, for routing purposes, with a first telephone switching system, but who is actually served by a second telephone switching system. The facility for carrying out this method is desirable in order to serve customers who need the advanced functions of a digital switching system, who are currently served by an analog switching system, and do not wish to have their telephone number changed when they switch to being served by the digital switching system. In accordance with the invention, a centralized database is queried to find the identity of the switch serving the called customer. The database returns a routing index for routing the call to that switch.
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