| 摘要 |
This invention provides an effective method and apparatus for testing the continuity of the shielding in communication cables, such as telephone cables, and for locating sections thereof which are defective and require repairs; without puncturing or damaging the cable insulation. The apparatus system embraces two identical probes designed for convenient application to the opposite ends of the splicing section to be tested. Each probe embraces a pickup electrode and an electronic impedance converting circuit. Noise signals induced on the cable shield from an exterior source, are capacitively coupled, through the cable insulation, to the pickup electrode on each probe, and then processed through an ultra high unity gain impedance converting circuit in the probe head and into a low impedance signal. The output from the two probes are connected through a switch to the input transformer of a measuring set which also includes an attenuator and appropriate operational amplifiers. A bridge rectifier meter circuit with an appropriate damping capacitor provides the means for measuring the signal level.
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