Privileg 861-M-NC / Litronix 1721R
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
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!
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.
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|
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:
On errors, for example dividing by zero, all digits are set to zero:
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...
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.
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.
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.
|Display||9 digit LED|
|Number of keys ||25|
|Functions||+ - * / % M|
|Entry logic (classification) ||ALG ((GBC))|
|1 + 0.000 = ||1.000 (the correct value would be 1.)|
|0 / 0 = ||Error |
|Power supply ||3xAA (internal)|
|Size||16,5 x 8,0 x 2,3 cm|