2. Signal boxes

Technology has evolved steadily from the first substations, which consisted of just a few mechanically-operated levers, to modern installations where a single signalman controls several hundred routes, spread over one or more substations.

Signal boxes have been particularly affected by the twofold evolution of increased radius and easier operation.

Technical developments have replaced mechanical substations with electrical substations, which in turn have been replaced by computerized substations, while at the same time route-controlled substations have replaced individual lever-operated substations, considerably improving performance.

Whatever their technology, switchgear units must ensure the same incompatibilities, so as to guarantee traffic safety (avoid collisions due to overtaking, nose-to-nose or slinging,...