A blower assembly for a pneumatic carrier transmission system including a first blower for supplying air; a second blower for exhausting air, wherein the first and second blowers are connected in series; and a dual passageway connecting device connected to and in communication with the first and second blowers, the dual passageway connecting device comprising a connecting tee having a tee inlet, a first tee outlet in communication with the tee inlet, and a second tee outlet in communication with the tee inlet, a first valve connected to and in communication with the first tee outlet, a first passageway connected to and in communication with the first valve, a second valve connected to and in communication with the second tee outlet, and a second passageway connected to and in communication with the second valve, wherein the first blower is operable to supply air through the first passageway and the second blower is operable to exhaust air through the second passageway. A pneumatic carrier transmission system including a first terminal; a second terminal; a transmission conduit connecting the first and second terminals in fluid communication with each other; a dual passageway connected to and in fluid communication with the transmission conduit; a first blower for supplying air to the transmission conduit; a second blower for exhausting air from within the transmission conduit to outside the transmission conduit; a first, non-controlled check valve connected to the transmission conduit for exhausting air from within the transmission conduit; and a second, non-controlled check valve connected to the transmission conduit for permitting air into the transmission conduit.