Inverters ICl-a and ICl-b form a multivibrator and ICl-c is a buffer. Inverter ICl-d is connected so that its output is opposite that of ICl-c; when pin 6 is high, then pin 8 is low and vice versa. Because pins 6 and 8 are constantly changing state, first one LED and then the other is on since they are connected in reverse. The light seems to jump back and forth between the LED`s, The 470-ohm resistor limits LED current
Depending upon the supply voltage used, the value of the resistor may have to be changed to obtain maximum light output. To change the switching rate, change the value of the capacitor.