| 摘要 |
PURPOSE: An apparatus for automatically selecting a passive line is provided to add and cancel dial signals with stipulated regulations, so as to securely perform an operation without supplying external power. CONSTITUTION: A telephone line incoming through a telephone line input terminal(6) is connected with a polarity corrector(7). The polarity corrector(7) corrects a polarity and applies the polarity to a next end of a circuit, regardless of an external telephone line connection polarity. A minus output end of the polarity corrector(7) is connected with one terminal of a C1(12) and one terminal of a telephone connection terminal(14). A plus output end of the polarity corrector(7) is simultaneously connected with one terminal of an L1(8), one terminal of an SW2(9), one terminal of a C2(17), and one terminal of an SW4(15). The other terminal of the L1(8) is simultaneously connected with one terminal of a C3(18), one terminal of a controller(10), one terminal of an SW1(13). The other terminal of the SW2(9) is connected with the other terminal of the C3(18). The other terminal of the SW1(13) is connected with the other terminal of the C1(12). The other terminal of the controller(10) is connected with the other terminal of the telephone connection terminal(14) via an L2(11). The other terminal of the SW4(15) is connected with the other terminal of the telephone connection terminal(14). The other terminal of the C2(17) is connected with the other terminal of the telephone connection terminal(14) via an SW3(16).
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