Pneumatic device connecting the towing vehicle to the trailer, comprising: - at least one pair of first couplings (2a, 2b) connectable to a first type of vehicles and one pair of second couplings (3a, 3b) connectable to a second type of vehicles, where each of said pairs of couplings (2a, 2b, 3a, 3b) comprises at least one supply coupling (2a, 3a) and at least one driving coupling (2b, 3b) connectable to the braking system (F T, F R) of the relevant vehicle; - at least one tank (4, 17) of compressed air; - at least one supply line connected to said supply couplings (2a, 3a) and at least one control line connected to said driving couplings (2b, 3b); - pressure variation means along said control line that can be activated/deactivated as a result of the connection/disconnection of said pair of second couplings (3a, 3b) to/from the relevant vehicle; characterized by the fact that said pair of first and said pair of second couplings (2a, 2b, 3a, 3b) are associated with a towing vehicle, where said pair of first couplings (2a, 2b) is connectable to a first type of trailers and said pair of second couplings (3a, 3b) is connectable to a second type of trailers, by the fact that said at least one tank (4, 17) comprises at least one towing tank and by the fact that it comprises: - a trailer-brake valve comprising a body in which there is at least one seat communicating with at least one loading line connected to said towing tank, with said supply line, the latter being in turn communicating with said loading line, and with said control line; - at least one distributor housed in a sliding manner inside said seat and movable at least to put said loading line in communication with said control line; driving means of said distributor, operationally connected to the braking system (Fv) of the towing vehicle and adapted to move said distributor to increase or decrease the passage gap of the compressed air coming from said loading line towards said control line to increase and decrease respectively the pressure in the braking system (F T) of the towing vehicle. - at least one pair of first couplings (2a, 2b) connectable to a first type of vehicles and one pair of second couplings (3a, 3b) connectable to a second type of vehicles, where each of said pairs of couplings (2a, 2b, 3a, 3b) comprises at least one supply coupling (2a, 3a) and at least one driving coupling (2b, 3b) connectable to the braking system (F T, F R) of the relevant vehicle; - at least one tank (4, 17) of compressed air; - at least one supply line connected to said supply couplings (2a, 3a) and at least one control line connected to said driving couplings (2b, 3b); - pressure variation means along said control line that can be activated/deactivated as a result of the connection/disconnection of said pair of second couplings (3a, 3b) to/from the relevant vehicle; - a trailer-brake valve comprising a body in which there is at least one seat communicating with at least one loading line connected to said towing tank, with said supply line, the latter being in turn communicating with said loading line, and with said control line; - at least one distributor housed in a sliding manner inside said seat and movable at least to put said loading line in communication with said control line;