What at first sight seems to just be a photograph of the centre exit doorway shows something more unusual on close inspection. This vehicle (and I'm pretty sure it was 111 but cannot confirm) had a photoelectric cell arrangement at this doorway - the two parts of it can be seen mounted on the vertical stanchions just below waist height.
I thought it was to open the doors automatically and was rather confused on the one occasion I travelled on it. There was certainly no information for passengers but I was already aware of it. With my more recent experience of "Schaffernlos" (conductorless) trams in Vienna I now realise it was part of a mechanism to close the door automatically. The cell prevented the doors closing if somebody was still trying to alight.
