The model 20AZV belongs to the “A” series. This class of machines includes for example the 20AT, 20ATG, 20AV. They were the very first “full automatic” Madas calculators. There are ten columns each of nine keys, numbered 1 in the bottom row to 9 in the top row. Thus, it is possible to set up any number of ten digits. Register I, the Product Register, displays the results of additions and subtractions and of multiplications performed by the machine. Its capacity is twice that of Register III, being twenty digits. Division with an automatic Madas is very simple. There is, just to the left of rows 6 and 7 of the keyboard, a key marked “:”. This is the Dividend Set-up key. The dividend is set to the left of the keyboard and this key pressed once. Immediately, the carriage is moved to the extreme right, and the dividend is transferred into Register I. The divisor is set on the keys just below the dividend. The Division-key, marked “Div” to the right of rows 7 and 8 of the keyboard is pressed. This starts the division, the quotient being recorded, digit by digit, in Register II.
A particular feature of this model is the split-lever for partial clearing of Register I. This lever is situated centrally on the carriage above Register I. When the lever is horizontal, normal clearing of of the entire 20 digits of the Product Register is operative. When, however, the lever is set in vertical position, dials 1 to 7 only may be cleared.
>On the front of the body, there is the “Register V”, also called Control-Register. This is necessary because, in full-automatic multiplication, the first factor in product has to be stored while the second is set up. Its capacity is also 10 digits. Moreover, a product formed in “Register I” may be transferred to the “Control Register” by operating a “Transfer-key”. This is a key marked by an arrow downward. The first picture here above, at left, shows this Register. The second picture, on the right, shows another special feature of the 20AZV. It is common to all “Z” models. These models have a tens-carry which extends to the full capacity of the Register. On the edge of the carriage, at left, we see 7 round sensors which move inside, according to the displacement of the carriage.
