The term 'BEEP, BEEP! SPEAKER' is a reference to the Roadrunner character from the Looney Tunes cartoons. The Roadrunner is a fast-running bird that is constantly chased by the coyote, Wile E. Coyote. The Roadrunner's signature sound is a loud 'Beep, Beep!' which is usually used to indicate its presence or to warn Wile E. Coyote of its impending arrival. This sound is made by a speaker, hence the crossword solution.