MK7302 schematic diagram probs

Hi,

A few time ago I bought an universal battery charger, I did the soldering and stuff. But my problem lies with the schematic diagram.
I understand the use for the Diode D1, and the capacitor C1. But I don’t know what’s the use for the 2 resistors and the transistor. I don’t see the link between them. So I called Velleman, and they said I had to ask it here, on the forum. So I hope that someone is able to answer my problem.

Thanks, Matthias

This simple kit is just a classic current source (sink to be correct). led voltage - BE drop divided by R2 value determines charge current.