Wikipedia
The UNITYPER was an input device for the UNIVAC I computer. It was an early direct data entry system manufactured by Remington Rand in the 1950s. The UNITYPER accepted user inputs on a keyboard of a modified Remington typewriter, then wrote that data onto a metal UNIVAC magnetic tape using an integral tape drive. The Unityper II was an input device for the UNIVAC II.
The Unityper II was a reduced-size, reduced-cost version of the Unityper I developed as a text-to-tape transcribing device for the original UNIVAC system. While it is shown as a peripheral for the UNIVAC II, it was developed for the original UNIVAC and released in 1953. Whereas the original required individual motors and control amplifiers to advance, rewind, fast-forward and maintain tension on the tape to be recorded, the latter was able to perform all of these functions using the electric typewriter's single internal motor via a flexible cable and clutch system.
Coding was accomplished via mechanical lift arms and latching bails added to the typerwriter's existing mechanical linkages in place for print-action. When a key was depressed, up to 8 affiliated lift arms were "caught" on latching bails which in turn connected 8 coding switches to the recording head. A commutator, powered by the internal drive motor, would momentarily complete the power circuit through the coding switches to the recording head before advancing the tape to the next recording position. When not encoding, a resistor balance network kept the recording head in an erase mode unless a rewind operation was commanded. This ensured a clearly defined magnetic space between bit patterns. Additional circuits prevented opening of the tape loading door once a tape was loaded.
Because the supply and take-up spools of the recording tape were no longer individually powered as in the UNITYPER 1, a mechanical solution consisting of a differential spring, ratching escapement and slip clutches was developed to overcome the problem of "differential moment" of accurately moving tape across the head. This was necessary because the supply reel is always decreasing in effective diameter while the take up reel is increasing in effective diameter as the tape moves from one reel to the other during encoding, and again when backspacing or rewinding.