From 230 V AC a DC supply of + 5 V is obtained. The power supply is given to the other blocks. The pulse generator at a particular frequency generates the clock pulses. The clock pulses are counted by a counter and gives output after every 10 pulses. The counter drives the transistors, which form the triac firing circuit. The transistors fire the triacs and they provide sufficient current to the load. Decorative bulbs are connected as load for each triac. The bulbs are sequentially turned ON and OFF in forward and reverse way.
The IC 555 works as the pulse generator and feeds the clock pulses to IC 4017. IC 4017 is the heart of this circuit. It works as a counter and gives the output after every 10 pulses. It drives the transistors, which in turn fire the triacs. The triac provides sufficient current to the load.