75.简答64D型继电半自动闭塞的FBD的黄灯电路为何要经过GDJ的前接点?
["\u7b54:FBD\u7684\u9ec4\u706f\u7535\u8def\u7528GDJ\u524d\u63a5\u70b9\u63a5\u901a\u662f\u4e3a\u4e86\u4f7f\u53d1\u8f66\u7ad9\u7684\u8bf7\u6c42\u53d1\u8f66\u4ee5\u540e,\u80fd\u53ca\u65f6\u5730\u76d1\u7763\u8f68\u9053\u7535\u8def\u7684\u5de5 \u4f5c,\u4ee5\u514d\u5f71\u54cd\u53d1\u8f66."]