Following Lotus’ use of DRD in British Grand Prix, Mercedes tested their updated DRD system in Germany GP practice. The basic idea of Mercedes DRD is similar to that of Lotus, although the mechanism for turning on/off the air switch might be different.
Instead of having two ears besides the airbox as Lotus did, Mercedes has two additional inlets at the back of airbox. This is easily fitted as Mercedes has integrated some removable design to their bodywork around roll hoop this season. The combination of a big and a small inlet may act as the control system for the air switch.
In terms of outlet, there are two outlets with the upper one below the main plain of the rear wing and lower one below the monkey seat/ beam wing. Above a certain high speed, such as long straights and high speed corners where less downforce is needed, the upper outlet switches on. The air blowing out under the rear wing disturbs the flow and therefore stall the wing for less downforce and drag. This would give an extra boost on the speed of the car.
Another noticeable detail is that both Lotus and Mercedes now have an extra small outlet below the rear wing. This is used to let out leaked air under the rear wing when the upper outlet is not supposed to be switched on.