SBB on 6/6, a new designation on 861, is a heavy shunting locomotive of the Swiss Federal Railways ( SBB). It is used primarily for operation on the hump.

The 1977 essential parts put into operation marshalling yard Limmattalstrasse was conceived in the hump operation for thermal traction. For the operation of a need of six locomotives was calculated. For this type shunting especially high tractive and a cab means are necessary. It should also be increased in case of failure of electric train with a powerful Dieselloktyp the reserve for assistance.

Technically originate from the On 6/6 from the experimental locomotives DE2500; they are in accordance with three-phase asynchronous traction motors and " Flexifloat " bogies (without pivot and the cradle ) equipped .. The SBB had in 1963 taken the initiative to build the overhead contact wire fed experimental Umrichterlokomotive with asynchronous traction motors. In close cooperation with the firm of Brown, Boveri & Cie. ( BBC ) in 1972 was the appropriate test vehicles are loading / put into operation 4 4 12001. The On 6/6 were now, thought based on the Be 4 /4 and the DE2500 as a further development step that / 6 II found its continuation in the heavy electric shunter Ee 6.

Six locomotives with the numbers 18521-18526 were ordered in 1973 and put into service in 1976. In the late 1990s their electronics were modernized. Today there are still five locomotives in use, the sixth ( 18524 ​​) was scrapped on 26 January 2004 and serves as a source of spare parts.