Self-addressing modules for programmable controller

In a module for a programmable controller, said module including logic circuits, enabling means for enabling said circuits upon receipt of an externally created module enabling signal, and conductor means on said module for conducting said module enabling signal to said enabling means, the improvement comprising:

• at least first, second and third input terminals arranged on said module in a preselected pattern having a first position, second position and third position;
• at least first, second and third output terminals arranged in said preselected pattern;
• said first input terminal being in said first position and electrically connected to said conductor means;
• said second input terminal being in said second position and connected to said first output terminal in said first position of said pattern;
• said third input terminal being in said third position and connected to said second output terminal in said second position of said pattern;
• said third output terminal being electrically isolated from said input terminals;
• and means for connecting said first, second and third input terminals to external first, second and third conductors, respectively, and an external decoding means for directing said module enabling signal to said first of said conductors only when said module is to be enabled and said decoding means directing said module enabling signal to said second and third conductors when said first and second output terminals, respectively, are to receive said module enabling signal.