System control for a printwheel typewriter

This paper presents the design goals and architecture of the IBM ®WHEELWRITER typewriters. Some of the development efforts and resulting technical innovations, such as a unique print hammer design which minimizes sensitivities to current variations, are discussed. Included is a discussion of a variable-reluctance stepper motor driver that has selectable damping. A novel scheme for initializing the printwheel and escapement motors is given; this includes sensing the font weight. The electronic architecture of the typewriter and the design of a simplified algorithm to handle the many different keyboards that can be attached to the machine with a minimum amount of data storage are explained.