The FN12-12 series indoor high-voltage load break switch-fuse combination apparatus are suitable for distribution systems with 12kV and below, operating at 50Hz AC. They are used for the control and protection of power equipment such as transformers, cables, overhead lines, etc. This equipment is particularly suitable for terminal substations in urban and rural networks, as well as prefabricated substations used for ring networks and double radiation power supply units, providing convenient and reliable protection compared to circuit breakers and other electrical devices.