Vr systems are systems that have helped develop Virtual Reality to what it is today. Although some of the earlier systems were crude and lacked a true sense of a Virtual Reality, they have all help to develop this growing field.
In 1923 Vladimie Zworkin designed and developed an electronic television camera tube. And in 1925 John logie Braid follow up Zworkin's when he was able to transmit and receive the first live moving images. Their developments are important in Virtual reality because they are the basis for the system today. like the HMD(Head-Mounted-Display) which uses two small screens that project moving pictures into the users field of vision to produce a sensation of being somewhere else.
Soon after, Edwin Link designed a carnival ride in 1929 which made the rider think they were flying in an airplane. This is the basis for today Flight Simulators. One other pioneer of the simulator was Morton Heilg when he developed an arcade game "Sensorama" in 1960 that used sight, sound, motion and even smell to make you think you were actually riding a motorcycle through the Brooklyn area.
The first HMD was invented in 1965 by Ivan Sutherland, his design tracked the position of the users head so the view points of a wire framed image that was being viewed to be changed. IN 1984 his work was contiuned by NASA when they used screens from Radio Shack's LCD Pocket TV for the first low cost commercial VR hardware and software.