The technology used would have been a combination of electromechanical controls, microfilm cameras and readers, all integrated into a large desk. Most of the microfilm library would have been contained within the desk, but the user could add or remove microfilm reels at will. A memex would hypothetically read and write content on these microfilm reels, using electric photocells to read coded symbols recorded next to individual microfilm frames while the reels spun at high speed, stopping on command. The coded symbols would enable the memex to index, search, and link content to create and follow associative trails.