Sentence:  Ernst gave a list of political activists who had been denied access to the air by private broadcasters, and pointed out that "Secretary Hoover's signature in New York sells for $150,000 to $200,000," thus limiting access to the <WSD>air</WSD> on the part of labor unions and other underrepresented groups. 
Meaning of the word marked with <WSD> tags:  A television or radio signal.