Background information:
ATB ev stands for Automatic Train Control Enhanced Version. This system is deployed since 2008 to supplement the existing ATB system.
The beacons are always located to the right of the right rail, with the long side parallel to, and almost tightly against the rail bar. Because of this asymmetric positioning system is also dependent on direction. They are typically mounted on a single sleeper.
A major advantage of this system is that it still operates at speeds below 40km/h. The original ATB system did not.
Architectural details:
ATB beacons are at fixed distances for a (light) signal which can issue a stop sign. The fixed distances are 120, 30 and 3 m for the corresponding signal. So these beacons do not appear in combination with pre-signals. When a train runs too quickly towards a stopsign, the ATB system intervenes to bring the train to a halt as quickly as possible. Only when the train stops completely, the operator can unlock and drive again.
