The Kramer VS-421 is a high performance 4x1 switcher for composite video and audio stereo signals. Using BNC connectors for video and RCA connectors for audio, one of four sources can be routed to one monitor, projector, or another receiving device. Two switching modes can be selected by a switch on the rear panel. In the vertical interval mode glitch-free transitions are provided when sources share a common reference sync, and in the immediate mode switching takes place instantly. The VS-421 can be controlled by front panel buttons or by shorting the corresponding pin to ground using a detachable block screw terminal connector on the rear panel. Video bandwidth exceeding 330MHz ensures transparent performance even in critical broadcast and production applications. Exceptionally high performance also allows the VS-421 to be used for SDI (serial digital) and high line rate video signals.