TECHNICAL  DATA  of  the  Electro-Mechanical  Calculator      CONTEX-20
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                                                          ( Model 10E )
Serial Number:       623994

Dimensions:   (ca.)  Width   =   8" /  20   cm
                     Depth   =  10" /  25.5 cm
                     Height  =   4" /  10   cm

Weight:       (ca.)  6 1/2 lbs  /  3.0 kg

Power Supply:        220 V AC / 15 W

Mechanics:           10-Block-Keyboard,
                     Serial-to-parallel Conversion
                     Rocking Segment Mechanism

Functions:           Add, Subtract, Multiply, Divide

Registers:           Input       =   10 Decimals
                     Counter     =    1 Decimal
                     Arithmetic  =   11 Decimals
Manufacturer:
                     BRDR. CARLSEN
                     Gentofte, Denmark
                     1962

R E M A R K :
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The fading PRINT in front says   » CONTEX-20 «
The LABEL under the bottom says additional  » Model 10E «  ...

                  

H O W   T O   U S E   the  CONTEX - 20
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( Picture from the  CONTEX - 10  Operator's Manual )

                          OPERATING CONTROLS

   1  Keyboard            5  Subtraction          9  Tabulator
   2  Clear               6  Position Marker     10  Addition
   3  Multiplication         & Correction        11  Control Display
   4  Division            7  Decimal Marker      12  Result Display
                          8  Return Key

START:
------
Press [C] key (2) to clear arithmetic & counter units.  Shift the red
slider (6) to the right to clear the input unit.

ENTER A NUMBER:
---------------
The actual number of digits entered are shown with the red slider (6).
If wrong digits are entered, push the slider right to clear the input.

ADDITION:
---------
Everytime a number is entered and the [+] key (10) is pressed, the
motor starts and the number will be added to the content of the
arithmetic unit (12).  THE INPUT IS "BLIND" !!!

REPEAT:
-------
To enter the same number more than once,  press & push to the left
[X] key (3) before pressing the [+] key (10).  The keyboard will not
be cleared.  To release the [X] key (3):  Press & push it right.

SUBTRACTION:
------------
Enter the number and press [-] key (5) to start the motorized procedure.

   NEGATIVE RESULTS are displayed in the arithmetic unit
      as the COMPLEMENT of the next higher 10, 100, 1000, ...

      Example:  -12  =  99...9988

MULTIPLICATION & DIVISION:
--------------------------
Because the counter unit has only  O N E  decimal,  multiplication &
division is tricky,  and needs to   k e e p   t r a c k   of numbers
either "IN MIND or ON PAPER" ...

MULTIPLICATION:    123 x 45  =  5535

Press [C] key to clear arithmetic & counter units.  Shift the red
slider to the right.  Lock the [X] key ...

Enter the multiplicand (=123).  The multiplicator (=45) has two digits.
Press & hold the [+] key until the counter will show  (with its
BLACK FIGURE)  the figure of the multiplicator's "1"-position (=5). 
Press the tabulator [ <- ] key.  Press & hold the [+] key
until the counter will show (with its BLACK FIGURE) the figure of the
multiplicator's "10"-position (=4).  The result (=5535) is in the
arithmetic unit.

DIVISION:          22 : 7  =  3.14285714  Remainder 2

Press [C] key to clear arithmetic & counter units.  Shift the red
slider to the right ...

Enter the dividend (=22).  Press the tabulator [ <- ] key until the
decimal marker is on its left position.  Press the [+] key to transfer
the input into arithmetic unit.  Enter the divisor (=07).  Press the
tabulator [ <- ] key until the decimal marker is on its left position.
Lock the [X] & [DIV] keys.  Press the [ -> ] key to start the motorized
subtraction of the divisor.  When the motor stops, the  RED FIGURE
shows the 1st digit (=3) of the result.  Pressing the [ -> ] key again,
the NEXT DIGIT will be calculated and shown as the RED FIGURE. Continue
until the maximal number of digits are calculated. The remainder (=2)
is shown in the right window of the arithmetic unit.

REMARK:  RELEASE THE [DIV] KEY, IF THE DIVISION PROCEDURE DOESN'T STOP

                      Have a look at "Calculating Trickies" ...
R E M A R K S :
=======================================================================
Two lines of interesting and innovative mechanical calculators came on
the market under the name  » CONTEX «  in the '50s and '60s :

The first was a key-driven adding machine in style of a Comptometer,
with a "half" keyboard and simplified mechanism:  CONTEX-A  & CONTEX-B.

The second was a series of 10-Block-Keyboard machines. The CONTEX-10 is
a manual one.  This  CONTEX-20  is motor-driven.  The  CONTEX-30  has
improved motor-driven multiplication and division. The  CONTEX-55  has
its own DIVISION REGISTER to complete the division full automatically.

impressum:
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© C.HAMANN         http://public.BHT-Berlin.de/hamann          03/26/08