AKA: fx-20, SCIENTIFIC CALCULATOR, AKA (Label): fx-20, Product number (P/N): fx20 (fx-20),
Keywords/Tags: fx20 (fx-20) | SCIENTIFIC CALCULATOR
Date of intro: 1975, Origin: Japan (List), Dimensions: 130x70x20mm,
Power: 3V: (AA x2), Adaptor: CASIO_adaptors: AD2S,
Display: Type = Display (VFD) (List), Digits = 8+1,
Number of keys: 32, #Key-Black: 11, #Key-Beige: 12, #Key-Grey: 7, #Key-Orange: 2,
Classification: / Pocket,
Featuring: Scientific functions, Square root, Logic-technology: VLSI (Very Large Scale Integration), calculator-on-a-Chip,
Related with: CASIO_docu: (Broch.) FX20: Introducing scientific slim...; CASIO_docu: (Ad.) *: Heute muß... (C100P,CD813,CM607,FX20,FX101,P810); CASIO_docu: (Ad.) *: Der Blitzgescheite... (CD813,FX20,FX101); CASIO_docu: (Broch.) *: Die Qualitätsrechner met großer... (fx20,fx101); CASIO_docu: (Cat.) 1976~ (Japanese); CASIO_docu: (Ad.) *: Zwei Beispiele aus dem größten... (FX20,Y800); CASIO_parts: (Box) FX20,
Main Components: CASIO: B8C1A,
Resemblance with: (Resemblance 096C),
Known Serial-numbers: 3155615 | 3364610 (List of all S/Ns from CASIO)
Initial Cost Price: 11500 JPY (€ 93,15), Collector value: 7/10,
Courtesy of: CALCUSEUM (Serge DEVIDTS),
Info: DUDEK Emil:
This model is the missing link between the older machines like the fx-10, which had an incomplete function set, to the more mainstream fx-29 and fx-39 style models.
it really is quite a nice little calculator, much smaller than you would expect. it fits neatly in one hand. you can almost use it with the same thumb.
This palm-sized style reminds me of the hp 20 series, like the hp-25. when pocket sized really meant it.
Quaintly, it has the small zero digit of early CASIO machines like fx-10 and the memory 8r. like the older machines, this one operates only in degrees and also hms->h is provided but not the other way.
interestingly, natural log shares the same button as x^y. clearly x^y is implemented by continuation from ln by a multiply and e^x. not a bad way to save a button assuming you won’t be testing y for integer.
improving on the fx-10 are trig inverses; arcsin, arccos and arctan, a memory (mc, mr, m+), change sign and, at last, proper exponential number representation. ie. x*10^y. displayed as usual with a 2 digit exponent.
Curiously, the exponent can only range to +/-39 inc. missing features are; 1/x, pi, and the antique a^n operation.
Some thought has gone into the keyboard layout, the x^y and ln sharing feature and the two = buttons, one is simple = and the other =M+. when you're not using the memory,
you can hit either button making quick calculations quicker.
Calculation speed is an improvement over previous models, rather than flicker and twitch for some time, only the right most digit flickers during scientific calculation and not for too long.
The machine only works to eight digits with no guard. trigs display 7 digits, e^x, six and ln, 8. basic calculations and square root are also 8.
You can’t seem to enter more than 6 digits with an exponent because after the sixth digit is entered, exp is ignored.
Trigs stop at the magic 1440 degrees, except for cosine. for some reason, cos accepts input up to 1530. a bug? maybe but the results returned are correct.
With the rear of the case removed you can bend out the main cpu board for examination.
Notice the cut-out hole for the glass display tube vacuum seal, which in this case is not needed as the pip lies above the board. You can also see the mini-board to the left with the high voltage power supply components on for driving the display.
The keyboard assembly can just be seen at the bottom if the picture.
Internet: Link-1: CALCULATORCOLLECTION