Digital automatic coupling (DAC) is a type of railway coupling developed in the 2020s to replace the English buffers and chain couplings, initially in Europe.
It resembles the Scharfenberg coupler with extra contacts to join electrical circuits (power, detection and control) and air hoses. [1]
Automatic couplers are categorized into five different levels in general.
For the DAC the function levels are narrowed down to specific functions. The function level DAK-3 must connect the ECP brakes. The function level DAK-4 must connect the e-coupler including electric supply (400 V) and digitial sockets. The function level DAK-5 must allow for remote uncoupling using an electric motor (the DAK does not use uncoupling air pipes as defined in EN 16019 for high-speed trains). Rollout plans may use function level DAK-4 when prepared for an update to DAK-5. [2]
In addition to uncoupling from the driver's cab, the DAK must also enable uncoupling while moving on the shunting hump. In addition to a mechanical device using a cable pull/uncoupling lever, the demonstrator also had an electrical device with switches on a control panel attached to the side of the car. Further development should enable electrical uncoupling both from the train and from a tablet or hump computer. This is essentially software development with high safety requirements. [3]
Couplings based on AAR and SA3 already have automated mechanical couplings, so some of the advantageous features of DAC are lessened. These have a maximum draw gear load well in excess of that possible with the DAC, say 1800 m instead of 750 m.
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