This machine belongs to the most advanced fully-automatic Madas, the “B” models, like 20BG, 20BVG, 20BS, 20BZS, 20BTG and 20BTZG. It allows fully automatic positive or negative multiplication and fully automatic division with variable or constant factors. Instantaneous automatic transfer of products (a*b*c), also for raising any number to any power.
Lever for disengaging automatic carriage return after multiplication, to facilitate following this immediately with division. Split clearance in product register, enabling individual and accumulated products to be shown at the same time.
By turning the lever over dial 9, automatic clearance can be disconnected from the 8th to the 20th dial in the “Product Register”. If this is done, dials 1-7 will clear themselves, whilst dials 8 to 20 will accumulate in multiplication.
An early version of the 20BVG exists with the same name, but it is a typical “A” model. The name should be “20AVG”, but no trace of this codename was found in H.W. Egli’s documentation.
The first version of this model has a small lever beside the key III, to engage a negative multiplication, while the later versions have a short red bar near to the long multiplication bar. The first version is rather close to the models “A”, while the more recent version is a real standard model “B”.
On the real “B” type of this model, to the left of the “Stop” key, there is a small lever (Non -entry lever) which allows to disable the “Register II” for all operations except the Division. To the right of the “DIV” key, another small lever (inverting lever) allows to get into the “Register II” a quotient in negative form. This control may also be used to enter multipliers negatively in “Register II“.