| 摘要 |
PURPOSE:To improve the search efficiency in the reception side and search surely a pair of objective cores without interfering with the communication of another current line, by transmitting a search signal across a pair of cores and the earth and across a pair of cores simultaneously. CONSTITUTION:Since the signal having a frequency f2 of an oscillator 12 is given across a cable core L1 10 and the earth, the transmission signal level due to electrostatic connection to a search line probe 17 is reduced in inverse proportion to the length. At this time, since the signal having a frequency f1 of an oscillator 2 is applied across the cable core L1 10 and the earth and across a cable core L2 11 and the earth with opposite polarities, the signal voltage of the frequency f1 is considerably lower than that of the frequency f2. Consequently, the tone of the frequency f2 is increased according the search line probe 17 approaches a pair of objective cores, and therefore, it can approach a pair of objective cores easily. Next, if a changeover switch SW14 is turned to the cable core side, the signal having the frequency f1 of the oscillator 2 generates an output only when the probe 17 is pressed to objective cores L1 and L2. Thus, it is discriminated that search of a pair of objective cores is terminated. |
