Abstract: A pneumatic transmission system having a carrier automatic braking system contains a transport conduit having a first end and a second end and being capable of permitting the transfer of a carrier therethrough, a first station for sending and receiving a carrier located on one end of the transmission conduit, and a second station for sending and receiving a carrier located on the other end of the transmission conduit. A motor blower, capable of moving a volume of air through a conduit, is enclosed within a supply/exhaust branch which is connected to one of the stations. A valve, capable of closing, to thereby create an air block in the supply line, is also disposed within the supply/exhaust branch. The motor blower blows air to move the carrier from one station to the other. The valve is activated, after deactivating the motor blower, when the carrier is detected at some predetermined location along the transport conduit.