It's mainly applied in the distribution circuit of high short circuit current and motor circuit, as an infrequently operating main/master switch by manual, esp. applied to be installed in the more advanced drawout low voltage sets of device. Double-throw switch is applied in the making and breaking of infrequent double-throw switch. The switch is adopted with full sealed structure in order to improve working reliability and reliable performance); it's featured in special rolling & inserting type contact system. Every phase has this two groups of double breakpoint contact system. Two groups of contact system can be connected in series or in parallel which can meet different circuit with different current and requirement of different work catogories. The contact system can make current go through rollers, so every roller is endured less motor counterforce. During the movement process, the contact of roller and static contact has rolling and sliding friction, which can avoid welding. The operating mechanism has power spring, so the motion velocity of moving contact group is irrelevant to the operating physical force and operating speed. The operator is made up of the handle on the panel, the drive joint connected with handle, extension axis, coupling joint and drive axis. The extension axis and coupling joint are only used when the drive axis is not enough long. The switch depth installed in the sets of device can be adjusted according to the need of electric components sets of block mount, and quite flexible.