Aristo M 36

Aristo M 36
Aristo M 36

Description

The german manufacturer Aristo was more than 100 years known for their mathematical-technical devices, mainly slide rules. Not before 1972, the rise of electronical pocket calculators forced them to change their strategy, since it was forseeable, that the days of slide rules were counted.

1972 the first Aristo calculator was launched, and in the following years, many further inhouse developments came onto the marked and especially to the schools.

Although, or maybe since, those calculators were of a very good quality and thus rather expensive, Aristo did not survive very long on the market, and in 1979 already, the firm had to close.


... with grey glass cover and original wrapping
... with grey glass cover and original wrapping

The model M 36 described here in its first version, originates from 1974 from the best days of Aristo calculators. It was not only visually very appealing and got the german "Die Gute Industrieform" award, but it was also very well made and "Made in Germany".

The long case (which was quite heavy from the three AA cells inside) layed perfectly in the hand and on the desk, nothing was shakey or loose, the bright LED display gave a very good readability and the keyboard with its colorful distinctive and well-shaped keys worked reliably and much better than many "brand" calculators.


battery compartement
battery compartement

The M 36 was powered by three AA cells or by an external adapter. For changing the batteries, the case had to be opened by a coin, which led to visible traces on the case. Although this eliminated the risk of losing the battery cover, this construction was a bit unlucky and the only weak point of the while calculators.

Inside, the mainboard was shielded and was connected with detachable wires to the two battery compartements - an expensive detail, which was not found in many other calculators.

As CPU, the Rockwell A 1241 was used; the three LED modules were driven by three ICs by ITT: two times an XK 1695A (week 36, 1974) and one ITT XK 1696 (week 34, 1974).


inside
inside

The electronic assembly wasn' really contemporary for 1974, since it looked as if it contained lots of manual work. But visually, it's a pleasure for every electronics freak.


LED modules with three digits
LED modules with three digits

The LED display was a bit unusual: Unlike using ready-made LED display lines, the display used here was made out of three individual LED modules with three digits each. This leads to two minor spaces in the display, which can be seen here:


display in full use
display in full use

The keyboard was on the back side of the mainboard and worked with double contacts, leading to mostly bounce-free and reliably usage. Only after more than 30 years now, it can happen sometimes, that a key slightly bounces, but that's a common thing even on the best vintage calculators - except HP and Casio. So, no use for worrying.


keyboard plate
keyboard plate

The calculation functions of the M 36 were rather simple, since it was more or less the entry model of the whole series. It is only capable of the four standard calculations and percentage.

The way, Aristo implemented the memory logics, is quite remarkable: For writing a number into the memory, you have to press the keys "M" and "+" in that order. Now a dot on the leftmost digit indicates the filled memory. Every subsequent "M" "+" or "M" "-" sequence now adds to or subtracts from the memory. Pressing "M" and "=" can recall the memoty and "M" and "C" will delete it.

The M 36 has got a constant function too, which uses the first keyed-in value as constant: If you for example enter 5 * 3 =, you will get the result "15". If you now enter 6 =, you will get 30, since the "6" is now multiplied with the formerly first keyed-in number "5". For division, it works the same.
You have to admit, that this is not really intutive.

A further speciality is the "X<->Y" key, which replaces the current number with the result of the last calculation. It is remarkable, since this key is not described on the manual on the back of the calculator:


manual on the back
manual on the back

On the displaying of the results, the M 36 has got another speciality: With a switch, you can select, if the result is displayed with two fixed decimal places, or as a true floating point number.


two fixed decimal places
two fixed decimal places

true floating point display
true floating point display

A minor and rather academical "bug" can be found on this calculator: When you calculate 1 + 0.000, you get "1.000" as result and not just "1." as expected, which means, that in this case, the suppressing of unused zero digits does not work. This is a very common "bug", which can be found on many calculators, but which has no relevance on your practical work.


overflow / error
overflow / error

Made in Germany - this once meant true quality items. Unfortunately this mark had its price - it just was too expensive to stand against the japanese competition, so that those fantastic calculators were availably only for a short peroid of time and thus are real collecibles.



Technical data

ManufacturerAristo
ModelM 36
Year1974
CPURockwell A1241
Display8+1 digit LED
Number of keys 20
Functions+ - * / % M x<->y
Entry logic (classificationALG (CC)
1 + 0.000 = 1.000 (the correct value would be 1.)
0 / 0 = Error
Power supply 3xAA
Size14,9 x 6,0 x 1,7 cm
Serial Number342
ConditionA-
Factsheet


Links
Aristo M 36 (de) (Very interesting page of the online museum of Prof. Dr. Jörn Lütjens)
Datamath: Aristo M 36 (en) (Description of the M 36)
Rechnerlexikon: Aristo (de) (Information about the manufacturer Aristo)