Two astable 555 timers of different frequencies are used with the slower one gating the output of the faster one. The 555 charging capacitors are buffered through op-amps and use blue LED's to display their charging cycle progress. Other LED's are used to display the various binary output states. NAND gates are used for gating and output inversion. The NAND gates sink current for the LED's even though the ground connections are not shown.
