| 摘要 |
PURPOSE:To achieve a simpler measuring circuit, a higher accuracy and the like by stopping the time counting in response to changes in the signal value at an input terminal to detect the disconnection position of a transmission line using the time counted. CONSTITUTION:A cable to be detected is connected to a line 5. A step pulse is sent to a cable 10 from a step pulse generation circuit 2. At the same time, a measurement start signal is generated on a line 4 from the circuit 2 makes a time counting circuit 9 start the time counting operation. The step pulse applied to the cable 10 propagates via the cable 10 and a reflection occurs at a point of disconnection caused in the cable. A reflection voltage generated at the disconnection point returns to the input end of the same cable part. The reflection voltage turns to the input end overlapping the step pulse, the voltage at the input end jumps. This voltage transit is detected with a peak voltage detection circuit 7. The time involved is the elapse since the application of the step pulse and a measurement stop signal is generated on the line 8 from the circuit 7 to halt the counting action of the time counting circuit 9.
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