Special attention was paid to sound levels in the passenger cabin and crew's stations; accordingly the engines were fitted with exhaust collector rings and long tailpipes, to reduce exhaust noise inside the hull.
12.
DSL Rings technology combines the capabilities of DSL bonding, Resilient Packet Rings ( RPR ) technologies and add-drop multiplexers ( ADM ) in a collector ring instead of the historic tree and branch approach.
13.
In its USAF tenure, many B-25s received the so-called " Hayes modification " and as a result, surviving B-25 often have exhaust system with a semi-collector ring that splits emissions into two different systems.
