| 摘要 |
A line control system adaptable to a facsimile machine having access to a plurality of foreign telephone exchanges with different busy tone specifications for detecting a busy telephone signal in which a busy tone specification corresponding to each of the plurality of telephone exchanges is stored in a memory whether a dialed telephone number is associated with a respective one of the foreign telephone exchange is determined. The busy tone specification corresponding to the respective foreign telephone exchange is accessed from the memory based on the determination; and a busy signal received from the respective foreign telephone exchange when the dialed telephone number is busy is compared with the accessed busy tone specification to determine whether the busy signal is a valid busy signal.
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