Challenge Predict circuit function (Only for beginners)

Challenge for beginners......
Predict the circuit function of the below circuit and post your reply here. If you can't just download the PDF with circuit functioning. Don't go for the PDF, just relax and try to understand the circuit, if you don't know the ICs search it in google and try to reply back. If you don't get it , its ok download the pdf.
test yourself.

(Note its not for the folks who can read this circuit as a peace of cake, i know there are lots of people can solve this in a fraction of second, this is not for you guys)

guys it is just a simple circuit, just try to reply....

But you said only beginners!

D1 and R3: are they not superfluous? E