Abstract: The invention relates to control devices for electrical, hydraulic or other forms of decelerator for heavy vehicles. For the purpose of avoiding skidding of the wheels of the vehicles when empty, in the case of a false maneuvre by the driver, the devices comprise means for automatically neutralizing the brake when the deceleration of the vehicle exceeds a predetermined level of the order of 1-3 m/s.sup.2.

Abstract: A control device for an eddy current retarder having a plurality of energizing windings comprises an insulating support carrying a plurality of connecting terminals for connection to the retarder windings and a junction terminal for connection to one pole of a power supply. A plurality of contactors are provided for controlling the energizing of the retarder windings, each contactor corresponding to a connecting terminal and comprising first and second fixed contact members, a bridge contact co-operating with the first and second fixed contact members, and a pull-on contactor winding controlling the bridge contact. A first contact plate connects the first contact member of each contactor to the corresponding connecting terminal and a second common contact plate connects the second contact members of the contactors to the junction terminal. Each contactor winding is connected to a respective control terminal which is connected to a control selector for consecutively energizing the control terminals.