Detection of obstacles in railway tunnels - surface wave line and wave generator connected to end of line

摘要

A surface wave line is fixed in the space,a wave generator is coupled to one end of the line i.e. 'line input', and the signal received at the other end of the line i.e. 'line output' is detected, also reflected signals at the 'line input'. The line or lines are arranged longitudinally along the tunnel so that the effective section of the generated wave (section of cylinder in which the quasi-totality of energy is confined) covers the total transverse section of the tunnel. The output and reflected signal detectors are coupled via an amplifier which controls an alarm device, so that a reduction in energy of the output signal or the appearance of a reflected signal, initiates an alarm signal.