Functionally, the current stairs are identical to upper slabs, as both share the property of being able to transfer wire upwards.
To differentiate them from slabs, allow stairs to act as two-way diodes.
If a redstone signal is fed into one flat end of a stair, it transfers to the other.
Both levers are switched on. However, only the lever feeding into the flat back of its stair is powered.
A redstone torch powers the bottom flat end of the stair. The flat back is powered, but the front is not.
The lever powers a wire which in turn, powers the stair. Only the repeater on the flat back is powered.
The lines are ordered from left to right. The lever powers the 2nd and 3rd lines of redstone. Since the 2nd line rests on stairs, the 3rd line is unaffected by it. Both the 1st line and upper 3rd line are powered by the 2nd line's stairs, whereas the lower 4th line is powered directly by the lever and has no delay.