Working on one of the 24 sectors of the e.m. and hadronic calorimeter. The UA2 central calorimeter extended over a region of polar angles from 40° to 140° (wrt beam axis) each sector covering an azimuth interval of 15°. Starting from its inner part, a sector contained trapezoidal e.m. (lead/scintillator) and hadronic (iron/scintillator) detection elements. The light collected through wave-shifter plates was brought to PMs on the outer surface (centre of the photo).