Machine control system

In a machine control system of the type comprising a programmable controller, a display screen, and means for displaying any selected one of a plurality of separate screen images on the screen, the improvement comprising:

• means for providing a positive check that the screen and the displaying means are operating to display the selected screen image, said check providing means comprising:
• means for generating a plurality of screen image codes, each included in a respective one of the screen images such that both the screen image and the respective one of the codes are displayed on the display screen together;
• means for sensing the screen image codes and for generating a code signal in response thereto;
• and
• means for comparing the code signal with the screen image code for a displayed one of the screen images and for indicating any disparity therebetween to provide a positive check of the screen and the displaying means.

In a machine control system of the type comprising a controller, a display screen, and means for displaying a plurality of separate screen images on the screen, at least some of said screen images comprising a set of switch labels, each switch label positioned in a respective label region of the screen image, the improvement comprising:

• an array of switches mounted on the front panel in physical alignment with respective label regions of the screen images;
• a mode control switch having a set of common poles, each connected with a respective one of said switches, a set of first output lines, and a set of second output lines, said mode control switch operative to interconnect each of the switches with a respective one of the first output lines when the mode control switch is in a first state, and to interconnect each of the switches with a respective one of the second output lines when the mode control switch is in a second state;
• means for connecting the first output lines to the controller such that the switches provide respective input signals to the controller when the mode control switch is in the first state;
• and
• means, independent of the machine control system, for connecting the second output lines to a machine controlled by the control system such that the switches provide respective control signals for the machine independently of the controller when the mode control switch is in the second state, thereby bypassing the machine control system.