The full fleet will comprise 21 two-car units of Class 483, referred to as "quarter trains", and 85 four-car units of Class 484, referred to as "half trains". Each unit has a full driver's cab at each end. Units of both classes can work in multiple with each-other, allowing services to be run with trains of two, four, six, or eight cars in total as required. and the weather-proofingincluding the
hermetic sealing of much of the power electronics equipmentis especially configured to guard against ice and snow ingress. The units' traction systems are designed to a high level of redundancy. Each vehicle in each unit is equipped with its own independent traction converter supplying the traction motors that are fitted to three out of the vehicle's four axles. The new units incorporate a number of new features designed to improve accessibility and comfort. Notably, they are the first trains on the Berlin S-Bahn to have air-conditioning fitted in the passenger saloons; due to height limitations imposed by the network's
structure gauge, part of the system is installed under the vehicle floors. Wheelchair spaces are provided adjacent to each driver's cab, with folding ramps available at the relevant doors. The exterior faces of all passenger doors have been painted black, to better contrast with the ochre-and-red coloured bodysides, and LED strips that illuminate green when the doors are open and red when they're closing are fitted at each door and vestibule. Audible indicators that sound when the doors are opening, and standing open, have been added in addition to the previously-required doors-closing alarm, which has been changed to match the European-standard warning tone used on mainline railways.
CCTV is fitted throughout the trains, which can be remotely accessed by the network security centre in the event that an emergency alarm is activated. Open gangways between the vehicles of each unit make it easier for passengers to move through the train, but internal doors are still provided should it be necessary to lock certain vehicles out of use. In addition to the front and rear destination displays carried by the previous Berlin S-Bahn fleets, the new units are fitted with side-facing displays at regular intervals along the train, and high-resolution internal screens that are capable of showing route diagrams and real-time journey updates. File:S-Bahn Berlin Baureihe 484 Führerstand.jpg|Driver's desk File:S-Bahn Berlin Baureihe 484 Innenraum.jpg|View through open gangway File:S-Bahn Berlin Baureihe 484 Mehrzweckbereich.jpg|Multipurpose area with tip-up seats File:S-Bahn Berlin Baureihe 484 Fahrgastinformation.jpg|Internal information display ==History==