In the latest in a string of acquisitions aimed at expanding its digital advertising services, Microsoft said that it was buying Navic Networks, a maker of television advertising technology. It comes as other major online advertising companies like Google, Yahoo and AOL, and start-ups like Spot Runner, are attempting to bring to television many of the qualities of online advertising: lower cost of production, better targeting and better ways to measure results. Navic, which is based in Waltham, Mass., and has about 80 employees, makes technology to create interactive ads. It also runs an advertising network that helps media buyers place ads on television shows. Terms of the deal were not disclosed.