 DTC was also studied in Baader's 1989 thesis, which provides a very good treatment of the subject.The first major successful commercial DTC products, developed by ABB, involved traction applications late in the 1980s for German DE502 and DE10023 diesel-electric locomotives and the 1995 launch of the ACS600 drives family.ACS600 drives has since been replaced by ACS800 and ACS880 drives.