Logic 1. In an actual electronic circuit, this means that for a  voltage to be present at the output, the AND gate circuit has to  receive voltage at both of its inputs. As pointed out, there are  different arrangements of electronic components that yield  this result. Whichever is used is summarized and presented  as the AND gate symbol. The truth table in  Figure 11-64 illustrates that there is only one way to have an output of  Logic 1 or voltage when using an AND gate.  putting output through a NOT gate. The NOR gate truth table  in  Figure 11-67  shows that the NOR gate output values are  exactly the opposite of the OR gate output values.  The NAND gate and the NOR gate have a unique distinction.  Each one can be the only gate used in circuitry to produce the  same output as any of the other logic gates. While it may be  inefficient, it is testimonial to the flexibility that designers  have when working with logic gates, the NAND and NOR  gates in particular.  Another common logic gate is the EXCLUSIVE OR gate.  It is the same as an OR gate except for the condition where  both inputs are Logic 1. In an OR gate, there would be Logic  1 output when both inputs are Logic 1. This is not allowed  A NOR gate is similarly arranged except that it is an inverted  OR gate. If there is to be a Logic 1 output, or output voltage,  then neither input can be Logic 1 or have input voltage. This  is the same as satisfying the OR gate conditions and then  The AND, OR, and NOT gates are the basic logic gates. A  few other logic gates are also useful. They can be derived  from combining the AND, OR, and NOT gates. The NAND  gate is a combination of an AND gate and a NOT gate.  This means that AND gate conditions must be met and then  inverted. So, the NAND gate is an AND gate followed by  a NOT gate. The truth table for a NAND gate is shown in  Figure 11-66  along with its symbol. If a Logic 1 output is  to exist from a NAND gate, inputs A and B must not both  be Logic 1. Or, if a NAND gate has both inputs Logic 1, the  output is Logic 0. Stated in electronic terms, if there is to be  an output voltage, then the inputs cannot both have voltage  or, if both inputs have voltage, there is no output voltage.  NOTE: The values in the output column of the NAND gate  table are exactly the opposite of the output values in the  AND gate truth table.  Input Output Input$_{A}$ Input$_{B}$ Output A 0 0 1 1 B 0 1 0 1 0 1 1 1 The  OR  gate Input Output Input$_{A}$ Input$_{B}$ Output A 0 0 1 1 B 0 1 0 1 0 1 1 0 The  Exclusive OR  gate Input Output Input$_{A}$ Input$_{B}$ Output A 0 0 1 1 B 0 1 0 1 1 0 0 0 The  NOR  gate Input Output Input$_{A}$ Input$_{B}$ Output A 0 0 1 1 B 0 1 0 1 1 1 1 0 The  NAND  gate Figure 11-66.  A NAND gate symbol and its truth table illustrating  that the NAND gate is an inverted AND gate.  Figure 11-67.  A NOR gate symbol and its truth table illustrating  that the NOR gate is an inverted OR gate.  Figure 11-68.  An EXCLUSIVE OR gate symbol and its truth table,  which is similar to an OR gate but excludes output when both inputs  are the same.  Figure 11-65.  An OR gate symbol and its truth table.  11-28 EXCLUSIVE OR Gate NOR Gate NAND Gate OR Gate Another useful and common logic gate is the OR gate. In an  OR gate, to have an output of Logic 1 (voltage present), one  of the inputs must be Logic 1. As seen in  Figure 11-65,  only  one of the inputs needs to be Logic 1 for there to be an output  of Logic 1. When both inputs are Logic 1, the OR gate has  a Logic 1 output because it still meets the condition of one  of the inputs being Logic 1. 