SETI scientist Frank Drake believes that the chances of alien intelligences discovering Earth will rapidly decrease because we are generating fewer detectable radio and TV transmissions each year. More of our programming is being delivered by cable and direct-transmission satellite technology, which involve very little leakage into space. A corollary is that there may only be a fairly narrow time window for detecting other intelligent species by listening to their unintended transmissions. As the article notes, this means that SETI researchers may have to focus on other methods of detection, such as searching for beacons intentionally built by other intelligences who wish to be found.