(b) Splices. Conductors shall be spliced or joined with splicing
devices identified for the use or by brazing, welding, or soldering with
a fusible metal or alloy. Soldered splices shall first be spliced or joined
so as to be mechanically and electrically secure without solder and
then be soldered. All splices and joints and the free ends of conductors
shall be covered with an insulation equivalent to that of the conductors
or with an insulating device identified for the purpose.
Wire connectors or splicing means installed on conductors for direct
burial shall be listed for such use.