CIRCUIT ARRANGEMENT FOR INDICATING THE OPERATION OF A VARIETY OF INDIVIDUALLY ACTUABLE SWITCHES OF A FUNCTION SELECTOR KEYBOARD

摘要

A function selector has an indicating unit which contains several identical groups of switches. All of the switches are connected with a control input of a microcomputer via a common control conductor. Each group of switches is connected to a different data input of the microcomputer by means of an identification conductor common to all switches of the group. An indicating shift register is associated with every group of switches and each switch of a group, as well as its corresponding light source, are connected to a different stage of the respective indicating shift register. An activating shift register is connected in parallel with each indicating shift register. The stages of the activating shift registers are connected with respective function generating elements. The microcomputer has a series of data outputs each of which is connected both with an indicating shift register and the corresponding activating shift register. Logic elements are interposed between each group of switches and the corresponding input of the microcomputer and insure that the respective input receives a different signal when a switch is open than when it is closed.