Resumen de Los sistemas ATC y APB en la conducción automática de trenes
Three concentric systems make up the automatic control of trains. These systems are: safety margins, operational data and automatic piloting. The transmittal of safety margins has a dual aspect depending on whether one refers to the geometry of the track or the relationship between the trains running. The supporting media for this transmittal can either be the rail or the cable, the latter holding more advantages. Depending upon whether the transmittal is by rail or cable, different frequencies are used and furthermore, the cable transmits a greater volume of data as a function of the greater range of frequencies it permits. Some areas exist where no special transmittals have to be made and here, for economic reasons, the rail is used as supporting media. At singular points the transmittal is carried out by cable. The A.P.B. system (absolute permissive blocking) allows for interesting new possibilities in automatic operation and signaling. This is a symmetrical signaling system. The rail circuits fulfil several functions with the perfect safety: covering the traffic in circulation, transferring the three positions of each signal to the line, ensuring the correct directional coupling and issuing information to the Cab Signal. The basic feature of the A.P.B. system is a rail circuit. The line of the A.P.B. rail is used as supporting media for the transmittal of safety margins.
For entirely new lines with no prior signaling whatsoever, where there is an increasing idea of automation and increasing traffic demands, the S.C.A.R. safety system will be chosen. This system is based on the principle of separating the possibility of "safety" and traffic control and the possibility of changing from the classic system to a completely automatic one. The S.C.A.R. system is based on the principles of the A.T.C. system (for train safety), the A.T.O. system (complementary orders) and the P.A. system (automatic piloting).
By superimposing the earlier fundamental principles we shall arrive at the point of a total line automation but each system can be implemented separately thus obtaining different degrees of automatic, controlled manual and free operation.
