Power circuit

OK here is the diagram so far and i will post the link again to clarify the need for the LED, And i now know what the 'L' in '78L12' means. thanks for that as for the 1N4004 on the dc input, it was in several example circuits i have seen in the past and i just assumed it was protection against reverse polarity connection, BUT as i said i am very in-experienced in the hardware side of things so if im incorrect then please tell me as this is one big lesson for me and i want to learn.

**broken link removed**