| 摘要 |
<p>PROBLEM TO BE SOLVED: To omit work of inspecting the growth extent of trees which makes insulation clearance to ground of a transmission line insufficient and to perform cutting work systematically. SOLUTION: Transmission iron towers 1a, 1b have a transmitting element 4, which transmits a signal for forming a signal emission line 3 of electromagnetic or ultrasonic wave having directivity and a receiving element 5 for receiving the signal, downward transmission lines strung between the transmission iron towers 1a, 1b. Then a means for detecting a change of a received signal to be generated through blocking of with the path of this signal emission line 3 caused by the crossing of the tip of a tree 10 with the signal emission line 3, is provided on the side of the receiving element 5.</p> |
