The 121 series trains are highly versatile trains capable of running on high-speed and Iberian gauge tracks manufactured by CAF and Alstom. They are equipped with a gauge change device and can operate at two voltages (3 kVdc and 25 KVca) with a maximum speed of 250 km/h on electrified lines at 25,000 volts of alternating current at 50Hz and 220 km/h on electrified lines at 3,000 volts of continuous current.

S-121 trains are single class and have a total of 281 seats, including one for people with reduced mobility.


121-series trains are an upgrade of S-120 trains. They consist of four carriages with 281 seats in a single class distributed across 4 carriages. Each carriage has a luggage area for large or heavy objects, as well as wide roof racks above the seats all along the compartment.

S-121 trains are equipped with monitors that allow images, videos and additional information to be displayed about the train's journey, next stop or speed, etc. and the seats feature individual audio jack and an additional reading light.

It features an air conditioning system with both hot air and cold air supplied through the ducts located at the top of the compartments.

Each carriage has two passenger rooms, separated by the central access platform. The reclining seats feature a footrest, coffee table, folding arm, plug and audio connection with controller to select different channels.

It features a carriage adapted for the use of people with reduced mobility. The size of its platform is greater than others, a toilet adapted to the most recent regulations in force, room access doors that are greater in size to facilitate the passage of wheelchairs, and a special location for these chairs that includes an automatic anchoring system, coffee table, plug, audio connection and intercom for communication with the train's staff. Furthermore, the special equipment for people with reduced mobility includes a wheelchair position, with the corresponding anchoring, designed for passengers with reduced mobility travelling in a conventional seat.



The structure of the body is self-supporting and has been made using lightweight aluminium alloy. Its design draws on aerodynamic and drive resistance concepts. It has buffer stops on the couplings, deformable structures and anti-climbers to reduce the consequences of a head-on collision for the passengers and for the vehicle itself.

The wall and ceiling lining is made of phenolic resin. The sides are slightly curved, to enhance the aesthetics and are equipped with fixed reflective glass windows. Armoured windows and an anti-shard panes are employed to improve safety whilst in movement. The line of the train is rounded off by skirts and fairings, both at the top and bottom.

The chassis is made from welded steel and the body rests on a load bolster, to which it is tightly fastened and under which the secondary suspension is mounted. Horizontal stresses are transmitted by a drag pivot.

Each unit has two driver's cabs, where the control and driving equipment is located on a dashboard and on a panel on the roof of the cab.

A single platform for each carriage provides access. Two outer doors, on each side, provide access to the platform, while two inner doors provide access to the rooms. Each outer door has a pneumatically operated folding footboard, which facilitates access to platforms of different heights.

Traction and auxiliary systems

The train, in terms of the traction equipment and auxiliary generation is conceived as two half-units. Each one is conceived as a train; therefore, it features all the energy capture, transformation and transmission elements required for the operation of the train. Each unit is autonomous from the capture to the transmission of power to the motors, the generation of low voltage and continuous voltage generation for control equipment.

Each carriage rests on two Brava type A1 bogies, with a single motor axle, meaning there are eight motor axles and eight carrier axles, which mean the gauge change manoeuvre can be performed at a speed of approximately 30 kilometres per hour. Each bogie has two axles, a motor and carrier, and both include brake discs; in addition, the motor is equipped with a gearbox. The motor axle is driven by a drive motor using Cardan-type transmission.

The drive motor, supplied by Alstom, is self-ventilating, asynchronous, features 6 poles and provides 512 kW on axle. The unit has 8 motors, 2 per carriage and each pair of motors is controlled by traction equipment. The IGBT traction converter ensures traction and electric braking, supplying each motor with the necessary power. Electrical braking can act regardless of whether there is voltage in catenary, thanks to the braking rheostats included in each power group.

They feature Caf's Cosmos control and monitoring system, the mission of which is to manage all train operations using different inputs and outputs, whether digital and analogue.

The driver-system interface is visible through a 10-inch TFT screen that graphically displays the status of the train's equipment and allows data and commands to be introduced.

It also shows any incidents that occur and provides the driver with recommendations or actions to be taken. Finally, the breakdown log of any equipment connected to the network can be downloaded centrally and remotely. It is also equipped with an anti-slip and anti-lock system.

Compressed air is produced in the two engine cars with driver's cab, using rotary compressors that provide a flow rate of 1,350 l/min. at 10 bar.

The pantograph's lifting equipment is operated pneumatically, with a reserve tank having been conditioned, in case it is needed, and an auxiliary compressor is available in the event of insufficient pressure.

The air-conditioning equipment consists of one compact unit per carriage, providing 50 kW of cooling power and 26 kW of heating power. The system is reinforced by heating convectors on both sides of the passenger compartments and heating resistors for the toilets.

The air-conditioning system features electronic temperature control.

To travel nationwide, it adapts to all the signalling systems currently in use: ASFA 200/98, ASFA AVE and ERTMS.

Bogies and brakes

The bogies are one of the most distinctive elements of the train. All the bogies on the series of carriages are motor bogies and form part of the Brava system (self-propelled variable gauge rolling bogie), developed by Caf; they are mounted on two axles, one carrier and the other motor, which allow the railway vehicles to adapt to any track gauge. This operation is carried whilst in movement at the exchanger, allowing automatic adaptation to Iberian gauge or international gauge tracks in just 3 seconds.

The Brava system consists of two wheelsets that can move laterally, in a pre-defined way, on a non-rotating axle body. During movement, a double safety mechanism prevents the wheels from moving laterally. The wheelbase is achieved as part of a lock-unlock mechanism, automatically operated during the gauge change process.

Furthermore, each bogie is equipped with two sand ejectors, a pneumatic secondary suspension and brake installation, speed and anti-lock sensors, anti-slip shock absorbers and grounding. The bogie on the compartment side also features a tab greasing system, stone trap and an Asfa catcher.

Finally, worth note is the inclusion series of sensors on the bogie, known as the ATMS system, which monitors different parameters, including the temperatures or the conditions of the different mechanical parts of the Brava axis.

These series feature three brake systems:

  • Mixed, recovery and rheostatic electric brake.
  • Pneumatic brake disc.
  • Parking brake.

The electric brake is the priority system, to minimise the use of the pneumatic brake. The pneumatic brake is applied in addition to the electric brake to achieve the required braking effort. In case of emergency braking, only the pneumatic brake reacts, bringing the train to a stop at a maximum distance of 1,000 metres when travelling at 160 km/h, and at 2,700 metres, when travelling at a speed of 250 km/h. The wheels are solid, low-carbon, non-alloy steel with a surface-tempered rim.


The compartment carriages on this train feature Schafenberg automatic couplings with automatic trapdoor for concealment. The type of coupling between carriages is semi-permanent. The system allows 120 series trains to run double length.

Control system

This series has the on-board systems required for the ERTMS level 1 and 2 and ASFA types of signalling, to travel on the two types of lines for which they were designed, and can be adapted to run on other systems, such as LZB and Ebicab.

The 120 and 121 series trains feature the train-to-ground radio communication system and GSM-R, and also come equipped with the Cosmos command and diagnosis system with the TCN communication network.

It also has a system for control and monitoring temperature and acceleration in the bogies.

Technical Features

  • Builder: CAF, with Alstom motor.
  • Units: 12 S-120 (+16 S-120 and 29 S-121).
  • Minimum composition: 4 Mc-M-M-Mc carriages.
  • Gauge: Adaptable Iberian/International.
  • Voltage: 25 kV AC (international) and 3 kV CC (Iberian).
  • Power: 4,000 kW international gauge/2,500 kW Iberian gauge.
  • Engines - model: 8 asynchronous - Alstom MTA/550 H.
  • Converters: 4 with IGTB technology (+3 auxiliary).
  • Maximum commercial speed: 250 km/h international gauge and 220 km/h Iberian gauge.
  • Number of axles: 8 motor axles + 8 carrier axles.
  • Brake: Electric brake, pneumatic brake and park brake.
  • Coupling: Shanfenberg.
  • Driver's cabs: 2.
  • Gauge: 1,435 mm/1,668 mm.
  • Signalling: ASFA, Ertms and Ave.
  • Total seats: S-120: 238 (156 Standard + 81 First + 1 Reduced Mobility). S-121: 281 (280 single class +1 reduced mobility).

Dimensions and Weights

  • Train weight: 251.3 t.
  • Standard compartment driver carriage's weight: 62,3 t.
  • Standard middle driver's carriage weight: 63,1 t.
  • First-class middle driver's carriage weight: 63,6 t.
  • First-class driver's carriage weight: 62,3 t.
  • Total train length: 107.36 m.
  • Length of carriages with driver's cabin: 27.90 m.
  • Length of middle carriages: 25.78 m.
  • Body width: 2.92 m.