| 摘要 |
PROBLEM TO BE SOLVED: To perform the test of normality of a subscriber line, without operating a terminal for 'no ringing' communication service and without ringing a subscriber terminal. SOLUTION: The two lines of subscriber lines are short-circuited by switches S2 and S4, and measuring voltage lower than the voltage, with which the terminal for no-ringing communication service operates is applied to the short- circuited two lines from the voltage-dividing circuit by resistors R2 and R3. Then, the magnitude of the external voltage is measured with a computing element 5. Before short-circuiting the two lines of the subscriber lines, a resistor R1, which lets a discharge current of a magnitude that the subscriber terminal does not sound flow, is connected between the two lines by a switch S1 so as to discharge the capacity between lines, including the capacity of the subscriber line. Moreover, before the start of testing, the switch S3 is switched off, to stop the power supply to the subscriber terminal 4. COPYRIGHT: (C)2004,JPO
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