LinkedIn Signal was retired on July 29, 2013. The LinkedIn team is continually working on developing more useful products and features. This sometimes means we will incorporate a feature into another product or remove it completely.
Although this feature is no longer available, you can still search for people, companies, keywords and jobs you are interested in directly from the search bar at the top of your LinkedIn homepage.
Hashtags (#) typed into updates will no longer link to Signal results.