CONTEX  -  20



REMARKS TO THE RESTORATION PROCEDURE:
Cable & plug were detoriated and had to be replaced with new ones.
The red DECIMAL POSITION MARKER was missing and had to be home made
from an old red toothbrush grip with a brass base to fit on the post.

Have a look at the plans and the result ...



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 :
-----------------------------------------------------------------------
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
**************************************
( 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

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.beuth-hochschule.de/~hamann      03/24/08