Two-part case with open front. Front panel (as accessory) can be inserted into the front guide grooves. Guide ridges and fastening pillars for mounting of PCBs in top and base.
Version IV: with battery compartment for 1 x 9 V flat battery (PP3) or 2 x 1.5 V mignon cells (AA).
Supply: 1 top and base part, battery compartment lid, assembly kit.