Visible crew/equipment: In the initial scene, when the Federation invade Naboo, you can see two takes of Queen Amidala watching the window on her palace. At the left of the screen you can see a black wire - maybe a light connection? (00:20:55)
Visible crew/equipment: In the Boardroom in Otoh Gunga, as Obi-Wan and Qui-Gon turn to leave, you can see Obi-Wan's lapel mic just inside his tunic.
Chosen answer: According to "Inside the Worlds of Star Wars: Episode I" by Kristin Lund, they are "laser doors which lock into position in response to potentially lethal power outputs that occur intermittently during plasma activation process" (the fight takes place in a plasma energy processing plant). There are six laser doors in deference to an ancient Naboo legend in which Chaos is held back by six inpentrable gates. As you say though, they're really just a plot device to add dramatic tension to the duel!
Sierra1 ★