A design for a small multi-service Bo-Bo locomotive, with speed up to 90 km/h (56 mph), had been devised by Giuseppe Bianchi as early as in the 1930s, but the project had been halted by the introduction of the E.326 and E.428.

After the realization of the 6-axle E.636, it was however decided to revamp the project by adapting to it some solutions already in use on the E.636 (engines, bogies, suspension etc.).

Mass production, however, could begin only after the end of World War II, part of the funds provided by the United Nations Relief and Rehabilitation Administration program.

The driver simply selects the combination (series or parallel), and the relative rheostat contactors are automatically and gradually closed by this system; in case of failure, the driver can manually rotate an apposite wheel (that also usually rotates automatically as the system advances) to proceed with the exclusion.

However, because of safety issues and the imperfect reliability of this system (there were no instruments indicating the status of the slave locomotive, so it was not certain if it correctly made a transition or not, for example), it was abandoned and then disassembled.