The cable branch box is used solely for cable branching purposes. The primary function of the cable branch box is to connect or transfer cables, mainly serving the roles of cable connection and cable transfer.

With the advancement of the cable grid development, when small capacity independent loads are distributed relatively集中ly, cable branch boxes can be used for multi-branch cable connections, as the branch boxes cannot directly operate on each circuit.

1) Cable branching function. On long lines, using multiple small-area cables often leads to waste, so in the transmission to power consumption, it is common to use main trunk cables. Then, as the cables approach the load, cable branch boxes are used to divide the main trunk cables into several smaller-area cables, which are then connected to the load. This wiring method is widely used in urban power grids for street lighting and power supply to small consumers.

2) Cable Transition Function. On a relatively long line, the cable length may not meet the line requirements. In such cases, cable joints or transition boxes are used. Generally, intermediate cable joints are used for short distances, but for longer lines, experience suggests that on cable lines over 1000m, if there are multiple intermediate joints, a cable branch box may be considered for transition.

Cable branch boxes are widely used outdoors. With technological advancements, more and more switch-equipped branch boxes are being introduced. Urban cable systems often employ dual-circuit power supply methods, leading some to directly refer to switch-equipped branch boxes as outdoor ring main units. However, most of these ring main units currently cannot achieve distribution automation. Nonetheless, manufacturers have now introduced outdoor ring main units that can be automated for distribution. This has begun to blur the lines between cable branch boxes and ring main units.