How do i make an item that can detect the redstone state of a block

I have been trying to make an item that can detect the redstone value of a block (on or off) and invert the redstone value either temporarily or permanently, however I cannot find any code blocks at all that are capable of detecting the redstone value of a block at all, I want to make it clear that I know exactly where the code blocks to change the redstone value of a block are, I simply do not know how to check for a redstone signal at all, pls help