The FKN12-12D pressure-operated load switch and the FKR12A-12D series pressure-operated load switch-fuse combination devices are suitable for three-phase distribution systems with a voltage of 10kv(12 kv) or below. They are used for the control and protection of electrical equipment such as transformers, cables, and overhead lines. They are particularly suitable for terminal substations and box-type substations in urban and rural networks. They are also applicable for the control and protection of ring networks and dual power supply units. The FKN12-12D series pressure-operated load switch can switch load currents and overload currents. The FKR12A-12D series pressure-operated load switch-fuse combination device can switch load currents, overload currents, and short-circuit currents.