The 3-in-1 base contains a fast shaper electronics interface (between the PMT and the pipeline dedicated to the pulse analysis), a slow integrator circuit (for measuring the current from Cesium calibrations and minimum bias events) and a Control Logic
The super-drawers: are located inside the back-beam of the calorimeter modules and contain the PMT blocks, the pipelines and the HV distributors. The electronics boards for the individual HV adjustments are connected on long bus boards mounted on the side of each drawer, while the digitizing electronics are connected to equivalent mother boards on the opposite side of the drawer.
Outside the super-drawers: the only electronics located in the electronics room, are the HV power supply, the Level-1 trigger, the RODs and the control electronics for the three calibration systems.