@mikebike: the output of the 4017 is 100% duty cycle. so that means if you have step one and step two on, they will lead right into each other and you'll have a step that is 2 cycles long. The output of the 555 timer is a 50% duty cycle. The AND gate combines the outs of the 4017 and the 555. The out of the AND is only high when both the 4017 and the 555 are high. SO it will go high when you set the step switch (from the 4017 out) on and for half a cycle because of the 555 50% duty. Make sense??? It's kind of confusing but relatively simple as far as logic goes.