The Kramer K304 20-00008290 is a secure 4−port KM switch. It allows an easy yet secure sharing of keyboard and mouse between four different security−level sources/computers. K304 provides the highest possible isolation between four connected computers. HSL Virtual Display Technology (VDT) switches the K304 seamlessly between computers once the mouse cursor crosses display borders. The K304 works smoothly with all operating systems, from Microsoft to Linux and Apple with no need for software installation.