Network system capable of implementing connection of two networks by using single-machine and single line

The utility model discloses a network selector which enables single computer surfs on double nets with single line. The selector comprises a switching device, a network card, a first hard disc and a second hard disc. Wherein, the switching device is connected with the first net and the second net as well as the network card; the network card is connected with the computer, and the switching device is connected respectively with the first hard disc and the second hard disc; the switching device comprises a control card, a switching switch and a converter. The control card is provided with a network cable switching switch for switching the network card and the first net and the second net, a power switching switch unit for switching different hard discs to connect with the power source. The device adopts the physical isolation, which can ensure safety of network data, and has simple installation convenience and reliability, and strong commonality, therefore, the device realizes one computer with functions of surfing on double nets through single line, and improves further the utilization rate of the computer and network. By adopting the device, double nets can be built through single line or the single line net can be changed into double nets, besides, the cost of network creation and network conversion is comparatively low, which is not only economic, but also convenient and feasible.