RCA Type 77-DX microphone

[1] Its popularity and classic design has resulted in the 77-DX becoming an iconic microphone, used by broadcasters and media personalities such as Edward R. Murrow, David Letterman and Larry King.

A rotating backshutter on the acoustic labyrinth, controlled by a screwdriver-operated slot at the rear of the microphone, allows the user to vary the microphone's pattern from omnidirectional in the fully closed position, to cardioid, to figure-8 (bidirectional) in the fully open position.

[5] The 77-DX has been used on countless vocal recordings by Bing Crosby, Kate Smith, Frank Sinatra, Elvis Presley, Johnny Cash, Al Green, and many others.

For example, with the microphone suspended, tilting it on the horizontal axis will cause the ribbon to sag slightly, resulting in a noticeable boost in the lower-midrange frequencies.

The pencil deflects a vocalist's breath as it reaches the microphone, and prevents it from hitting the ribbon directly.