IEC 309 BTS Range Extra-low voltage plugs and socket-outlets IEC 309 standard - The IEC 309 BTS range of extra-low voltage plugs and sockets for industrial applications enable machinery and devices that operate on voltages of less than 50 V to be connected.The range includes different versions – straight mobile, 90° connectors, surface-mounting and flush mounting, protected and watertight.Available for currents from 16 to 32 A.