The ASFA Digital(ASFAD) or Automatic Braking and Announcement of Signals system, processes information from the signals and sends it to the trains using beacons as transmission medium. The onboard system uses this information to generate corresponding control curves and acts on the brake when it detects that the supervised speed limit is exceeded.
The ASFA beacons installed on the rails provide early information of the nearest signal state in the train travel direction (early beacon) and passing signal state information (on foot signal beacon); also send level crossings signals information, speed limitations and signalling changes (AV-CONV).
The train feedback system consists of a resonant circuit, which oscillates at a certain frequency (permanent frequency, FP). When the sensor passes over a beacon, it begins to oscillate at the resonant frequency set in the beacon, and tunes with the beacon by inductive coupling, receiving the information of the corresponding signal state.
ASFA DIGITAL VIA ELEMENTS
The ASFA Digital (ASFAD) system consists of the following elements: