Abstract: A keyboard input device for printers, composing apparatus, or clear text display devices which employ type fonts that can be changed at will, has a group of multiple indicia bearing keys which can be positioned to bring a different set of indicia to a readable position to indicate to the operator the character make-up of the type font being used. Both manual and electrical mechanisms are provided to effect indicia positioning. Mechanism is also provided to interconnect indicia selection with either manual or automatic type font selection and changing. Each key operates an electrical switch which is connected to a diode matrix to provide coded output to the device under control.

Abstract: A type element interchange mechanism is incorporated into a high speed serial printer with rotary print wheel and linear carriage movement. A number of print wheels are selectively mountable onto a carriage, which carries a print wheel, print hammer, and print hammer solenoid, from one or more removable carousels, each carousel typically carrying several different type font print wheels. Print wheels are transferred directly between the carriage and a carousel, without the necessity of intermediate transfer mechanisms or steps, through the controlled linear translation of the carriage and the carousel. The print wheel-carrying carousel has a plurality of arms and is rotated to present the desired arm in position for transfer of a print wheel with the carriage. Microprocessor controls are provided so that print wheel changes are implemented automatically in response to input signals defining the desired font type.