Visual display unit with light pen access - has synchronising and counter based circuit combined with brightness control stage to vary brightness around access region

摘要

The visual display unit has a light pen input to identify positions with the raster pattern screen. The display includes a synchronising unit (SE) that has a synchronising signal input (BST) and the input from the pen (TO). Outputs (V1, V2) are generated and introduced into gates in a clock signal generator (ST). Other inputs are provided by a generator (LE) that responds to a light pulse identification signal (DE). A brightness stage (HE) and counter circuit (ZE) provide control of values transmitted by a multiplexer (MVX) that handles the display data (BD). ADVANTAGE - Improved display point brightness in vicinity of light pen.