The pneumatic controlled friction brake is activated in individual cars of the train set by means of a pneumatic signal. The signal initialized at the head of the train, is transmitted in the main brake line and reaches subsequent distributor valves, causing the brake to be activated in subsequent cars. Maintaining the required propagation speed of this signal is possible thanks to the accelerator function performed by the distributor valve. The article describes the original idea of accelerator construction. The results of experimental investigations of the accelerator function and the results of computer simulations of accelerator operation in the whole reference train have been presented.