6. Digital Signals and Logic Gates

Engineers know that it is easier to design two-state devices than multi-state devices. In logic systems, variables, circuits, statements, etc., can be treated in one of two distinct states: true or false, yes or no, on or off, present or absent, energized or not energized, conducting or non-conducting, high voltage or low voltage, and so on.

In digital electronics, we distinguish two distinct values of voltage, VH corresponding to the higher of the two voltages and VL corresponding to the lower of the two voltages. There are three ways in which we can assign binary values to these voltages:

1. Positive logic assignment: True [ 1 ] : VH False [0]: VL

2. Negative logic assignment: True [1]: VL False [0]: VH

3. Mixed logic assignment: Allow the designers to use positive
Or negative logic at any point in
Their design, as they desire.