Friday stops a phonograph's operation by gruffly tossing its stylus arm aside, and its tip bounces far off the rotating album. This shows that it was a manual phonograph, not automatic nor repeating. Because the stylus was midway through the album side, it gives an indication of how long the music had been playing, about 15 minutes. The two policemen could have deduced that the girl had just started the music.
When the four detectives are at the office building to catch the pornographer, one says that the office is up on the fifth floor. As Friday approaches the elevator, he pushes the down button.