| 摘要 |
PURPOSE:To discriminate the kind of call without using special numbers by counting the number of digits of dialed number, and discriminating the kind of call based on the result of counting. CONSTITUTION:When the subscriber A of an extension dialed, the dial number is accumulated in a register RET, and at the same time, the register RST counts the number of digits and reports the result to a central controlling unit CC. On receiving the number of digits, the central controlling unit CC discriminates the king of call by the number of digits. Here, it is supposed that setting is made beforehand to indicate mutual connection in extension by four digits and trunk line by seven digits. For instance, when the number of digits of dial number is counted with the result of seven digits, the kind of call is discriminated as main wire connection. Consequently, the central controlling unit CC catches a main wire trunk COT and makes connection to a trunk line.
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