Privileg 861-M-NC / Litronix 1721R

Privileg 861-M-NC
Privileg 861-M-NC

Description

The malaysian electronics manufacturer Litronix produced in the seventies a number of pocket calculator and sold them under their own name as well as licensing them for others, for example for the "Quelle" stores in Fürth, Germany. There, these calculators were sold under the name "Privileg" in the stores and in the famous "Quelle" catalogue.

One of these calculators is the Privileg 861-M-NC, a rather simple calculator with LED display, memory functions (hence the "M" in the name) and internal NiCD accumulators (hence the "NC" in the name).

The case of the calculator is in a console shape with a very good, almost HP-like, keyboard down on the plate, the 9 digit LED display above and on top lots of space for the three internal rechargable AA cells.

Those internal accus are a danger for vintage calculators, since on the inevitable (self-) dischargement, they start leaking within a few months. The electrolyte not only corrodes the contacts, but also destroyes cables and PCB tracks. Therefor, calculators with internal accus have to be recharged every few months!


inside view
inside view

The keyboard works with hinge-keys, which have got a good pressure point and work almost (except the "1" key on my calculator) bounce-free. Such a good keyboard was normally only found in very expensive calculators, for example on the HP spice series, but not in a chain store calculator. Compliment to Litronix here!

The only drawback of the keyboard construction is, that it is kind of "soldered" to the case. To put away the keyboard, you have to destroy the plastic solderings, which is a destructible process alas. At the end, you should re-solder the keyboard to the case, otherwise there's a gap on the upper side of the keyboard which can let dirt inside the case.


back view
back view

On powering on the calculator, the user will notice two specific features: Threre's no power-on switch, and the display presentation is a bit unusual.

The 861-M-NC is now powered on by a switch on the side, as usual on moust calculators, but by two keys on the upper left of the keyboard. The leftmost key "C/On" powers on the calculator or resets it, and the key "Off" next to it switches it off. This technique was quite prospective, since on many vintage calculators, the switches with their corroding contacts are often a problem - but not on the Privileg calculators.

The display presentation is quite unusual, since it works with two fixed decimals. After powering it on resetting, it therefor displays "0.00" instead of "0". And for saving power, the display starts blinking after 30 seconds without user activity.


display after power on
display after power on

The rule, that always two fixed decimals are shown is only valid for additions and other calculations, where the result has no more than two significant decimals. In practical use, this means, that it applies to all financial calculations.

The calculation power and the rest of the display is more or less equal to other pocket calculator of that time: As usual, 8 digits can be used, the ninth digit is used either for the decimal point (which uses a whole digit), the negative sign (which makes the first decimal digit of a number with seven digits before the point disappear), or for indicating an overflow:


Overflow
Overflow

On errors, for example dividing by zero, all digits are set to zero:


Error display
Error display

Regarding the calculation capabilities, the 861-M-NC is an absolutely contemporary, simple calculator, which only knows the four basic and percentage calculations. It has got a modern type of memory, which uses the four keys "M+", "M-", "RM" and "CM", which are still used on todays calculators. And if it did not have the correcting key "->", which can erase the digits one by one, you could think of working with an calculator of the year 2000 - so forward-looking was that calculator in 1974...


unknown CPU
unknown CPU

The CPU of that (almost) one-chip calculator is unknown, since it has no usable code on it. The second chip, an "LBC-1080", is also unknown, but might act as keyboard driver.


LED module
LED module

The LED module, which was cutting edge in 1974, was probably made by Litronix itself. For these modules, the compound illumination areas and the enormous magnifying lense, which made the tiny segments readable, were typical. The disadvantage of that was, that the display was unreadable even at tiny angles.


detail view
detail view

On that LED module, all connectors were bonded to the board, so that on the outside, there were only a handfull of mechanic uncritical soldering points. But if only one segment of one decimal failed, the whole display was unusable, since it was not repairable on the inside. In practical use, this hardly happend and was no real disadvantage, so that in the end, this was exactly the type of display, which was used for long time on many kinds of pocket calculators.

The only thing, which was quicky changed, was die position of the decimal point: It was attached to the individual digits and needed no longer a digit of its own. With that invention, it was possible, to show one more digit.

To sum it up, the Privileg 861-N-MC was a quite advanced and well constructed pocket calculator and belongs to every good collection.



Technical data

ManufacturerPrivileg
Model861-M-NC
Year1974
CPU
Display9 digit LED
Number of keys 25
Functions+ - * / % M
Entry logic (classificationALG ((GBC))
1 + 0.000 = 1.000 (the correct value would be 1.)
0 / 0 = Error
Power supply 3xAA (internal)
Size16,5 x 8,0 x 2,3 cm
ConditionA-B
Factsheet


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