Much work has been done into detecting potential signals from extra-terrestrials, but I want to discuss the more active approach of sending signals ourselves... What attempts at such communications have we attempted ourselves? I remember hearing of attempts to broadcast radio waves into space, which strikes me as too weak to attract an alien's attention, or the gold plaques on the voyager probes, which strikes me as rather... laughable. It seems to me that a potential beacon would have to satisfy a number of criteria. Speed: It must travel at around c. Else, it simply is not worth bothering with. By the time it is detected, we would be extinct. Magnitude: The signal must be powerful, as its strength diminishes at it spreads out by an inverse square law. Dust and so on may also absorb some. Coverage: We don't know where the aliens are. Therefore, we need a way of covering the entire sky, and signaling each spot for as long as possible. Universality: It needs to be a technique that a similar type of being would have anticipated and be prepared to detect. Any others? Any ideas as to how to (eventually) fulfill this? Based on our current standard of radio telescope, what is the maximum range of the signals we are sending out right now?