Distance education involves teaching students who are not physically on-site through various technologies and instructional methods. It began in the early 1700s through correspondence education and saw more development with the introduction of audiovisual technologies in the early 1900s. Television was later explored as an instructional medium in the 1930s and 1940s, though its potential was never fully realized. Studies found student achievement from television instruction was comparable to traditional face-to-face teaching.