The Kramer K304E 20-0001990 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. K304E provides the highest possible isolation between four connected computers. HSL Virtual Display Technology (VDT) switches the K304E seamlessly between computers once the mouse cursor crosses display borders. The K304E works smoothly with all operating systems, from Microsoft to Linux and Apple with no need for software installation. For enhanced security, a USB user authentication port (DPP) connects to a smart card or biometric reader. This requires the insertion of a physical authentication card or identification of a fingerprint to access the various computers/networks.