At this time, the Q0 output from pin 3 sets the LED brightness to 25% as determined by R14 (Figure 2). Each push feeds a clock pulse to IC2.14, which increments the count. The second push makes Q1 go high, with R15 now setting the second dimming level to 50% brightness. R14 & R15 inject a current into IC3’s feedback node to achieve the various dimming levels. The third push sets IC2’s unconnected output Q2 high (leaving Q1 & Q2 low) to set the LEDs to 100% brightness. The fourth push sets Q3 high, pulling down the bias of IC1 and allowing the whole circuit to enter sleep mode.