The European Train Control System (ETCS) has been specified and prepared within the last years as a new European standard solution for interoperability and cross-border operation in the European railway network. Now the first commercial application of ETCS Level 1 has been prepared, installed and put into operation on the Sofia – Burgas line at Bulgarian State Railways (BDZ). An important part of ETCS level 1 is the lineside subsystem consisting of the lineside electronic units (LEUs) and Eurobalises. In this paper, the solution for the lineside system developed by Alcatel TAS Austria for the Bulgarian project will be presented. This solution (Alcatel 6413 ALTRAC) was designed for a decentralised lineside system where the signal information is directly detected at the signals by measuring the lamp currents. For more flexibility of the lineside system in future applications, this solution is being extended by three new features: additional functionality by integrating configurable digitals I/Os, optional control of Euroloop, and the possibility for centralised control using a direct interface from the interlocking system to an LEU controller.