The supply of DC 6V from the solar panel is fed to the rechargeable battery through diode D1 (1N4007) and resistor R1 (15R). Diode D1 functions as a reverse current protector and resistor R1 limits the battery charging current to a safe value. Transistor T1 (BC548) is connected here as a circuit breaker to control the T2 LED controller transistor (SL100). T1 disables T2 when the circuit receives enough output power from the solar panel.