T E C H N I C A L   D A T A   of the  Mechanical Calculator   CONTEX-10
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                                                          Newer Version
Serial Number:       431027205

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

Weight:       (ca.)  6 lbs  /  2.8 kg

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
                     1960


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

                          OPERATING CONTROLS

   1  Keyboard            5  Subtraction          9  Tabulator
   2  Clear               6  Position Marker     10  Function Key
   3  Multiplication         & Correction        11  Control Display
   4  Division            7  Decimal Marker      12  Result Display
                          8  Return Key
   R E M A R K :
   *************
   THIS MODEL has a "Jump-To-Left"-Key  [ <-:- ]  right to the [0]-Key
   useful for DIVISION ...

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 to the right to clear input.

ADDITION:
---------
Everytime a number is entered and the FUNCTION KEY (10) is pressed,
the number is 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 function key (10).  The keyboard will
not be cleared. To release the [X] key (3): Press & push it right.

SUBTRACTION:
------------
Press [-] key (5) before pressing the function key (10).

   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 the function key as often as the figure in the "1" position -
The counter will show it with its BLACK FIGURE (=5).
Press the tabulator [ <- ] key.  Press the function key as often as
the figure in the "10" position - The counter will show it with its
BLACK FIGURE (=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 to shift
it to the left. Press the function key. Enter the divisor (=07). Press
the tabulator [ <-:- ] key to shift it to the left.  Press and lock
[DIV] & [-] keys.  Press the function key until the [-] key comes up
(= Underflow).  Press the function key again (= Addition/Correction).
Read the RED FIGURE: This is the 1st digit! THE FUNCTION KEY IS BLOCKED
NOW!  Press the [-] key.  Press the tabulator [ -> ] key.  THE RIGHT
DISPLAY CLEARED!  Press the function key until the [-] key comes up
(= Underflow) again.  Press the function key (= Addition/Correction)
again.  Read the RED FIGURE:  This is the 2nd digit! ... REPEAT ... 


The INSTRUCTION MANUAL (14 pages) can be downloaded from ...

                  http://www.rechenwerkzeug.de/Contex.zip

HELP for  "REPAIRING A BOHN CONTEX"  can be found in ...

                  http://www.csparks.com/contex

   ... together with useful links around this calculator.


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.  This  CONTEX-10
is a manual one.  The  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.

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© C.HAMANN       www.tfh-berlin.de/~hamann       impressum       11/12/08