During the Grand Prix weekend all cars must have at least four camera housings on specific location.
Housing location is determined by the rules as you can see in the illustration below and housing above the air intakes (4) must always contain a camera.
All cars must have two timing transponders supplied by the official timekeeper. These transponders allow the timekeepers to record every lap time of every car during the weekend and teams must ensure that the transponders are in working order at all times.
Their position is determined by the rules too – team can choose between three positions where they can place them (A, B and C).