The function of metal shield in cable and Heat shrinkable straight through joint is mainly used to conduct cable fault short-circuit current and shield electromagnetic interference to adjacent communication equipment. In running state, metal shield is at zero potential under good grounding state. When the cable failure, it has the ability to conduct short circuit current in a very short time. The grounding wire should be welded reliably, and the metal shield and armored belt on both ends and the cable body should be welded firmly.