mixer drive is flanged to the power takeoff of the internal combustion engine driving the truck mixer the truck mixer 10 has a control for the mixer operation the control has two operating systems 14 and 17 the operating system 14 has a three part structure and includes an operating lever 16 an operating part 18 with a pushbutton field 20 and a screen 22 and includes a console 24 with an emergency off switch 26 cf fig3 this operating part 14 is arranged laterally in the rear region of the truck mixer 10 as is shown in fig1 however a further operating part 17 is provided in the operator 39 s cabin which consists of a lower shell 28 and an operating part 30 this operating part has a similar structure to the previously named operating part 18 since it also has a pushbutton field 32 and a display 34 all the operating elements namely the operating part 17 and the operating elements 16 18 and 26 of the operating part 14 are connected via a bus e g a can bus to the hydraulic control to the travel motor control or to a separate motor control if a separate motor is present to a possibly present radio remote control and to an optionally present telematics system such as a gprs status indicator all the designated functions of the truck mixer superstructure should be operated and visualized using the operating system in total the operation can now take place at a plurality of positions at the truck mixer that is via the operating element 14 at the outside of the truck mixer optionally cable connected and additionally in the operator 39 s cabin via the operating element 17 the bus enables the communication between.