COMMUNICATING METHOD USING UNDERGROUND CABLE LINE

PURPOSE:To execute communication safely and exactly, by coupling a current transformer to a ground point of an underground cable line or a cable shielding layer, and making a circulating signal current flow between the shielding layers. CONSTITUTION:A current transformer 13 or 13' is installed to the circumference of a cable 11a in a read-end X or a connecting line 12x, and a signal current (i) consisting of a sound signal or a control signal is generated in a circulating circuit by a transmitter and receiver 14 connected to the current transformers 13, 13'. This current (i) passes through a shielding layer 11a of a cable 10a from the near-end X to a far-end Y, reaches the far-end Y, from which it passes through a connecting line 12y, also passes through shielding layers 11b, 11c of other cables 10b, 10c, is returned again to the position of the current transformer 13' or 13 from the connecting line 12x of the near-end X, and circulates in the circulating circuit. Accordingly, when a current transformer 15 or 15' is installed to the circumference of the cable 10a or the connecting line 12y, in the far-end Y, and the signal current (i) is detected by a transmitter and receiver 16 connected to this current transformer 15 or 15', a signal from the near-end X can be received in the far-end Y.