Page 67 - Computer science 868 Class 12
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2.1.2 AND Gate
                 AND gate requires at least two inputs and are called binary gates. It produces high output (1) only when all inputs are
                 high (1). In all other cases, low output (0) is produced. It is represented by a dot (.).
                 The symbol and truth table is shown below.

                                    A          B          A.B             A       B        C       A.B.C
                                    0          0           0              0        0       0         0
                                    0          1           0              0        0       1         0
                                    1          0           0              0        1       0         0
                                    1          1           1              0        1       1         0
                              Truth table of two variables AND gate       1        0       0         0
                                                                          1        0       1         0
                                                                          1        1       0         0
                                                                          1        1       1         1
                                                                      Truth table of three variables AND gate


                 Multiple switches connected in series form an AND                             +
                 gate. From the circuit, we  see  that the lamp  will                                            L
                 glow if both switches A and B are closed. If any one                          -
                 is open, electricity will not flow and the lamp will   Symbol of AND gate
                 remain off.                                                                   Switching circuit diagram
                                                                                                     of AND gate
                 2.1.3 OR Gate
                 OR  gate is a binary gate. It produces high output (1) when any one  input is high (1). Only when all inputs are  low , 0
                 is produced as output. OR operation is represented by plus (+).

                 The symbol and truth table are shown below.
                                    A          B          A+B             A       B        C       A+B+C

                                    0          0           0              0        0       0         0
                                    0          1           1              0        0       1         1
                                    1          0           1              0        1       0         1
                                    1          1           1              0        1       1         1
                              Truth table of two variables OR gate        1        0       0         1
                                                                          1        0       1         1
                                                                          1        1       0         1
                                                                          1        1       1         1
                                                                      Truth table of three variables AND gate
                                                                                                           A
                 OR gate can be implemented with two switches                                              B
                 A and B connected in parallel. If any one of the                                +                 L
                 switches or both are closed then electricity will                               -
                 flow through the circuit and the lamp will glow.
                 The lamp will  remain switched off when both     Symbol of OR gate
                 switches are open.                                                                 Switching circuit of
                                                                                                         OR gate





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