1 votes 1 votes Digital Logic digital-logic digital-circuits made-easy-test-series + – screddy1313 asked Jan 26, 2019 edited Mar 3, 2019 by ajaysoni1924 screddy1313 449 views answer comment Share Follow See all 4 Comments See all 4 4 Comments reply Shaik Masthan commented Jan 26, 2019 reply Follow Share Type the question instead of screenshot ! it is not 2-way switch, a 2-way switch depends upon state of other switch ! let initially both switches are off ==> BULB is OFF now at ground Floor, you switched on ==> irrespective of the state of first floor switch Bulb should be ON ∴ S1-ON, S2= either ON or OFF ==> Bulb should be ON now at ground Floor, you switched off ==> irrespective of the state of first floor switch Bulb should be OFF ∴ S1-OFF, S2= either ON or OFF ==> Bulb should be OFF now at First Floor, you switched ON ==> irrespective of the state of ground floor switch Bulb should be ON ∴ S2-ON, S1= either ON or OFF ==> Bulb should be ON S1 S2 BULB i) OFF OFF OFF ii) ON OFF ON iii) ON ON ON iv) OFF ON OFF v) OFF ON ON vi) ON ON ON vii) ON OFF OFF viii) OFF OFF OFF i) and viii) ===> ok iii) and vi) ===> ok ii) and vii) ==> contradicitng ==> take as Don't care iv) and v) ==> contradicitng ==> take as Don't care As taking K-map, there is only one literal which in true form ==> 0 NAND gates required ! 1 votes 1 votes Shaik Masthan commented Jan 26, 2019 reply Follow Share @screddy1313 what is the answer they provided ? 0 votes 0 votes screddy1313 commented Jan 26, 2019 reply Follow Share @Shaik Masthan they have given that above functionality can be implemented by using ex-or. So required nand gates are 4. But your ans made more sense than they provided !! 0 votes 0 votes Shaik Masthan commented Jan 26, 2019 reply Follow Share if it is a two way switch then it is EXOR implementation ! By the way edit this question as, type the question ! 0 votes 0 votes Please log in or register to add a comment.