The class DM motor cars and class D trailers were designed in the thirties by English Electric for the suburban network of Wellington. Each set consisted of two or three cars, one of which was a power car with four 150 hp traction motors. This also had a cab in the rear baggage compartment to use it as single car if needed, but that cab was later removed. Each set had a driving trailer on the other end, and some had an additional trailer. After the first order from 1936, more were ordered in 1942 and 1946 when additional lines were electrified, what led to a total number of 49 sets.

The two-car sets were mainly used for hilly lines, while the three-car sets provided additional capacity on flatter lines. In the seventies and eighties many were modernized, but the sets of the first batch were withdrawn from 1981 with the introduction of the new class EM/ET from Ganz-MÁVAG. After some minor refurbishments after the turn of the millennium, the last sets were withdrawn in 2012. Five complete sets and six single trailers have been preserved.