D1 is a Schottky Diode used to prevent battery charge escaping through the solar panel at night. Something like a 1N5817 (1 Amp 20 Volt diode) will do the job and it has a very low voltage drop of under 0.45 Volts. D2 and D3 are ultrabright LEDs used to illuminate the inside of the nestbox. R3 and R4 are resistors chosen (400+ Ohms) to ensure that no more than 30mA of current gets to the sensitive LEDs, with R5 (a 10k variable resistor) used to increase the resistance and therefore dim the LED s if they are too bright.The LM317T is a voltage regulator * used to bring the voltage of the solar panel and batteries down to just over 8 volts using resistors R1 (270 Ohm) and R2 (1500 Ohm) to set this value. K is the wireless CCTV camera. A switch (not labelled) is used to manually turn the camera on and off as required.