| 摘要 |
A typical Private Automatic Branch Exchange (PABX) makes connections between a number of telephone instruments and an exchange line from the Public Switched Telephone Network. The present system can select the particular telecommunications service provider which is the most economic for a particular call. The system consists of the telephone instruments (1), the PABX (2), a microprocessor (3), a tariff memory (4) and a display (6) and keyboard (5). The display and keyboard can be used to reprogramme the processor and amend details in the memory.
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