Madas 20ATG has the same mechanical engineering as the model 20AT (see description of this model). It is dressed, however, in a new modern body, colour grey and square keys. This look will be on every later model, belonging to the “B” series (20BVG, 20BTG, 20BTZG, etc.). Like the 20AT, an additional register is fitted to this model. This is an *“Accumulator Product Register”*, generally named *“Register IV”*. It can be cleared only by means of a *“thumb-lever”* to its immediate right.

Whereas, normally, *“Register I”* clears automatically before the formation of each new product, *“Register IV”*, as its name implies, accumulates successive products. It may be disconnected by moving the lever situated on the machine-casing to the left of *“Register III”*. Therefore, the carriage is complex, generally named *“Triplex”* (see descriptions of models 20AT, 20BTG, 20BTZG).

There is very few differences between model ATG and model BTG. For example, 20ATG has a small “+/-” lever at the bottom left of the keyboard, to control “negative multiplication”, while on the BTG, this lever has been replaced by an extension of the Multiplication bar, sometimes of the same colour, sometimes finished in red.

*Register IV*are rounded off, on the third digit from the right, according to the figures of digits 1 and 2. When the lever is in the lower position, the numbers provided to the

*Register IV*remain exactly the same. There is a movable flap which can hide the first two digits, because these digits are not significant for the user when the rounding is activated.

First of all, we see that, each time

*Register II*is cleared, manually or by the operation need, the figures 2 and 1 of

*Register IV*are set to 5 and 0.

Suppose now that you engage a multiplication, let us say:

**3.45 x 7**The result in

*Register I*is

**24.15**. In the

*Register IV*, the result is

**24.65**, but with the flap hiding digits 1 and 2, we see only

**24**.

Now, compute the product of: **3.45 x 13**. The result in *Register I* is **44.85**. In the *Register IV*, the result is **45.35**, but with the flap hiding digits 1 and 2, we see only **45**.