The Southern Railway (SR) gave the designations 4-COR, 4-RES, 4-BUF and 4-GRI to the different types of electric multiple unit built to work the route between London Waterloo and Portsmouth Harbour. The 4-COR type units survived long enough in British Rail ownership to be allocated TOPS Class 404.

Electric Multiple Units (EMUS) are permanently coupled sets of coaches in which electric traction motors are mounted on the bogies of certain carriages — known as motor coaches — in each unit, so there was no need for a separate locomotive, and a …

4 Cor units were built in two lots; 3101-3129 in 1937 for the Portsmouth Direct route and 3130-3155 in 1938 for Mid-Sussex route. The 4 Res units for the Portsmouth Direct service were numbered 3054-3072 and appeared in the spring of 1937.

The 4-Cor units introduced by R.E.L. Maunsell were the second generation main line electrics and these units eliminated one of the major operating deficiencies of the 6 Pan/6 Pul, which was the lack of gangways between units.

In 1937 29 4-COR units (4-car Corridor units), numbered 3101–3129, were built at Eastleigh Works.to work the route between London Waterloo and Portsmouth Harbour. Corridor connections were provided throughout each unit, including between units.

The 500 series classes were reserved for miscellaneous DC EMUs not from the Southern Region. This included the DC (third/fourth rail) lines in North London, Manchester and Merseyside and the OHLE lines in Greater Manchester.

The second batch in 1938 comprised thirteen four‑car corridor units with buffet car (4 BUF) and a further twenty-six 4 COR sets, these being intended for use on the lines electrified under the Portsmouth No.2 electrification scheme. However, some of these units also saw use on the Brighton line from the outset. © Glen Woods collection Unit ...

Unofficial classification, also referred to as 6HIT (Hitachi). Unit numbers were allocated from 1001, following the 1–1000 set numbers of semi-fixed formations of hauled coaching stock. Different types of unit were given numbers:

4COR 3142 is the Southern Electric Group’s preserved electric multiple unit, built in 1938 for the Southern Railway. We also have a 5th COR vehicle in our care. The 5 vehicles are: 4COR Vehicles

SR 4-COR EMU at Broad Street station in November 1970, on the L.C.G.B. 'Southern & North London Electric Train Tour'. The 4-COR was loco-hauled over the 'gap' between SR and the LMR electrified lines, which had recently been converted from '4th-rail' to '3rd-rail' DC.