This is a good buildable and simple clock with only 2 observers.

I personally find it very useful for bsp. if you want to build a trap with a clock, it is on the one hand very space-saving and on the other hand, it is well suited for beginners. But you also need the right ingredients for 2 observers. Unfortunately, it is therefore quite costly.

Instructions:

You place the two observers with their faces looking at each other. And your clock is ready. It has one drawback, you can't change the speed of the signal.