Uses two transistors in back to back mode to alternatively switch the charging and discharging of capacitors. When the circuit starts up the transistor that switches on first will cause a discharge in its adjacent capacitor. When the one capacitor is discharging this raises the voltage on the base of the transistor to switch on one LED as well as charge the second capacitor. This then repeats the charge/discharge cycle of the second capacitor turning off the first LED and turning on second LED.
