This page is for learning more alternative ways to build redstone contraptions as well as getting better at it. This website will include lots of circuts to use when buiklding redstone.
The pulse extender increases the amount of ticks it takes to unpower. For instance, pushing a regular wooden button takes 10 ticks to to stop powering again. So, what a pulse extender would do is increase the tick delay from 10 to a greater number. There are different variants of pulse extenders which could have a longer or shorter pulse.
For a combination lock you need to have levers (or and form of T-Flip-Flop) and they must be either up or down. For example, you have 5 levers attached to a combination lock the code has to be UP, DOWN, DOWN, UP, DOWN in oreder to have a redstone output. If any of the levers are are not in the correct position y ou will not have an output. Place a torch directly be hand a lever if you want it down, place redstone dust behind a lever if you want it up.
A T-Flip-Flop converts a button, or anything that goes on then back off, into a button havong the characteristics of a lever. Pressing a button oncce will usally turn something on then off again. With a T-Flip-Flop, when you press the button it will send an output and it will stay powered on until you press it again. When you press the button again the output will power off, just like a lever.