hi there i am quite reforumlating this into demorgans law thanks in advance
(All INVERTED)
(a inverted) (b inverted) (c inverted) (none inverted) - -
A.B.C + A.B.C + A.B.C + A.B.C

thanks its for a 3 input alarm. If 2 or more inputs and on then the output is on

thanks ed

 

Could you make it more clear which one is inverted?

 

[attachmentid=1021] I'm Assuming this is what you want whenever there's 2 input on, output is high.

[attachmentid=1023] This is the answer I have for you, just learned in my class 2 days ago.

 

Here's an explanation on how I got the answer:

[attachmentid=1024] This is call K-Mapping which is covered in allaboutcircuits in Digital section.

[attachmentid=1025] This is the output that you wanted. I place a 1 on 011,101,110, and 111. Then I had them all grouped up accordingly in pairs. So now we have 3 pairs.

From there the answer is just simply: [attachmentid=1026]

Lookup K-Mapping in Boulean Algebra in Digital.