Otto Tower was an Illinois Central Operated tower and housed a Saxby and Farmer mechanical lever interlocking machine. Otto was one of several towers that IC had that had an Traffic Locking arrangement that would allow IC to each plant operate locally within CTC rules. The plant was manned until CTC was cut in between Otto and Gilman Illinois. The tower still stands today, boarded up with the old interlocking levers still inside. Today this tower belongs to the Canadian National Railroad.
Photo from the Union Switch and Signal Company Archives. Taken around 1920's. Looking North at Otto Tower before it closed. BX was the telegraph call sign.