Visible crew/equipment: After Kirk tells the policeman that he wants to see Merikus and "perhaps" he's a friend, the policemen lock the cell then leave, and when it cuts to a view of the cell from the side as Spock walks over to the steel bars, the overhead boom mic is visible inside the cell, over Spock. It's visible again, with a better view, when McCoy walks over to Spock beside the bars. (00:18:15)
Visible crew/equipment: Set lights are reflected in Spock's tricorder screen before he closes the cover.
Answer: Kirk was getting his physical and Dr. McCoy probably turned off communications, because if he hadn't, Kirk would have left and headed straight for the bridge, leaving McCoy irritated.