This series is originally based on the license of the Swedish company ASEA and the SJ Rb locomotive from Sweden.

The models with higher maximum speed have lower tractive power and are used for passenger or light freight trains only, whereas the models with lower maximum speed have high tractive power and are thus able to pull heavy freight trains.

Original livery of Yugoslav Railways was red (occasionally orange) and blue with white stripe and "Jugoslovenske železnice" inscription on it.

Locomotives of Republika Srpska have similar livery as the original Yugoslav, but with faded colours and a white stripe between blue and red.

The Romanian Railways' original livery was in grey with a red or blue stripe, some examples even with the Romanian tricolor flag used instead of the blue or red stripe (similar case to a few members of EA class), but after 2000, the traditional white-red (front ends) livery has been applied.

The Yugoslavian locomotives derived directly from the already renowned prototype ASEA RB1 improved in the mechanical construction under the RC1 series pattern.

[1][2] A number of locomotives have been modernised to Class 46, initially 3 units by Končar Group, and later by PROMAT and Softronic Craiova.