- " Very deliberately, he [Doc] walked in a complete circle around the [DeLorean time] machine. Then he withdrew a folded piece of paper from his pocket and handed it to Marty. / "After I fell off the toilet," he said, "I drew this. Does it look familiar?" / Marty unfolded the sheet and immediately recognized a crude but accurate sketch of the flux capacitor. / "You bet," he answered. "
- —From Back to the Future by George Gipe (quote, pages 122 and 123)
- "Marty passed Doc a long, rolled-up piece of paper that had been sitting in the car next to the letter [containing the repair instructions]. Doc unrolled the scrolled instructions and looked them over quickly. Yes, his future — or rather, past — self knew just what he needed. Now here was something he could understand!"
- —From Back to the Future Part III by Craig Shaw Gardner (quote, page 21)
A schematic diagram, or simply schematic, was a plan showing how a piece of technology worked.
Emmett Brown drew up a schematic diagram of the flux capacitor, the key to making time travel possible, on November 5, 1955. The idea had come to Doc in a vision he had after he came to following a mishap at home, when he slipped off his toilet and hit his head on the sink while hanging a clock in his bathroom.
Another schematic diagram was drawn up by Doc's 1985 counterpart, and put into the DeLorean time machine alongside the envelope containing the repair instructions he wrote after becoming stranded in 1885 when the DeLorean was struck by lightning on the night of November 12, 1955, before hiding the car in the Delgado Mine. This plan showed Doc's younger self how to build a unit using 1950s components — such as vacuum tubes — to replace the time circuit control microchip (shorted out by the lightning bolt) in order to repair the DeLorean so that Marty McFly could return to 1985.