An arrangement and a method for testing a telecommunications circuit over Dense Wavelength Division Multiplexing. The polishing step includes the steps of applying to the concrete surface a diluted silicate polishing compound, mechanically polishing the concrete surface with a rotary polishing machine, using pads or disks or drums, cleaning the concrete surface, and repeating said steps with polishing pads or disks of increasingly finer grit until the surface obtains an aesthetically desirable level of shine. Furthermore, one head section is canted with respect to a plane that is transverse to the first direction, such that the head sections write two adjacent tracks at different angles with respect to the plane. An increased scrolling speed and very short scrolling time can be realized, without adversely affecting image quality during a normal mode. This permits quick recombination of the positive electric charges accumulated at the drain and gate of the MOS transistor T1, at the gate of a MOS transistor T2, at the anode of a photodiode, and in a capacitor C2, and thereby makes quick resetting possible.