The British Rail Class 377 Electrostar is a British dual-voltage electric multiple unit passenger train (EMU) built by Bombardier Transportation on its Electrostar platform at Derby Litchurch Lane Works from 2001 to 2014. Description The trains work suburban services in South London, and main-line commuter services to Sussex, Surrey, Kent and the South Coast, on which they replaced 4Cig and 4Vep slam-door stock that was more than 40 years old and did not meet modern health and safety requirements. Built in the early 2000s, the units had a troubled introduction. Being fully air-conditioned, their higher power consumption compared to the trains they replaced led to major upgrades being required to the 750 V DC third-rail power supply used in the former Southern region. The collapse of Railtrack following the Hatfield accident further delayed this upgrade work, and the new stock did not enter squadron service until 2003. Class 377s are fitted with external CCTV. There is an open area for wheelchairs or prams, and both intermediate coaches have toilets. Bodyside power doors are electrically operated, a move away from the air-powered systems of previous generation EMUs. Dual-voltage units are fitted with a Brecknell Willis high-speed pantograph, incorporating a pair of aerofoils on the pan knuckle to steady the pan head against the OLE contact wire. The configuration of a 5-car Class 377 unit is: DMOC(A) – 2 motors on inner bogie, sander, auxiliary converter module MOSL – 2 motors on inner bogie, standard toilet (not found on 377/3s) PTSOL – pantograph, transformer, compressor, universal-access toilet MOS – 2 motors on inner bogie, standard-class interior (only found on Class 377/6 and 377/7 units) DMOS(B) – 2 motors on inner bogie, sander, auxiliary converter module In the 4-car units the driving cars are composite. The first-class saloon is between the driving cab and the first set of passenger doors. 4-car units also do not contain the MOS coach. Couplers The Class 377 use Dellner instead of Tightlock couplings used on the Class 375s. Southern's 375s were all reclassified to Class 377/3s upon conversion. These reclassified units can still be identified by their 3-car formation. Note that Southeastern's 375s (sub-classes 375/3, 375/6, and 375/7) were also later converted from Tightlock to Dellner couplers but were not reclassified. Its sub-class 375/8 and 375/9 units were fitted with Dellner couplers, as built. Traction current supply All units can receive power via third-rail pick-up which provides