Moisture supervision of telephone cables with synthetic insulation - employing moisture sensitive material separating two conductors connected to insulation resistance monitor

摘要

The appts is for telephone cables employing synthetic insulation on the individual conductors, and having transposed cores. In order to detect the presence of moisture, for example due to damage to the cable sheath, two conductors in the cable are insulated with a moisture sensitive material. When the cable is installed the two conductors are connected to an insulation resistance monitor which indicates a low reading if moisture is present. A variety of materials are suitable for the special insulation. Examples are salts or mixtures which form an electrolyte in the presence of water a felt material with high absorbent properties, or paper. Without the appts. as described the entry of moisture into a cable with synthetic insulation is difficult to detect before it enters a jointing box.