This circuit is composed of 16 pcs LED (light emitting diode). The 16pcs LED divided into four groups, and each group has different flashing frequencies, when four groups flash together, this item looks like a small Christmas tree. The circuit is powered by a 9V battery. Advantages: This circuit is simple and practical, low power consumption.It uses integrated circuits for driving: fewer parts,and the line is simple and easy to understand. External Wiring Kit: With pluggable plug for easy replacement of parts at any time and conducive circuit debugging. Also allows us to deepen our understanding of the principles of the circuit in the debugging process. This line is in the form of the oscillation circuit by the cycle generated by the following principles: - after the first charge, the capacitor C1 & C4 charging is complete. - capacitors C2 & C3 will continue to charge. - when the transistor Q1 & Q4 is turned on at the same time, it discharges the capacitor C1 & C4. - capacitors C2 & C3 is fully charged, the transistor Q1 & Q4 will be closure, while also charging the capacitor C1 & C4 again. - transistors Q2 & Q3 is turned on while the capacitor C2 & C3 will be discharged. - By analogy, the flash of speed is the oscillation frequency, and the frequency is determined by the resistor R & capacitance C values. - Board Size:70mm*110mmProducts from Bazhou's store