What are the most basic components I need to generate and recieve a radio signal and how would I arrange them? For instance imagine I want to make an LED in my bedroom flicker when my front door opens. Firstly how would I make this happen at the most basic level, so that some signal is recieved and secondly how would I amplify this signal so that, for instance, the light stays on for 5 seconds? I'm guessing for the latter I just need to learn how a 555 chip works so I'm more interested in the former question. Thanks in advance.