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Have a Look INSIDE the CONTEX-B ...

T E C H N I C A L   D A T A   of  the  Mechanical  Calculator   CONTEX-B
This Danish calculator is a small and light-weight    "HALF-COMPTOMETER"

Serial Number:       0203419

Dimensions:   (ca.)  Width   =  9    " /  23 cm
                     Depth   =  9    " /  23 cm
                     Height  =  2_3/4" /   7 cm

Weight:       (ca.)  3 lbs  /  1.3 kg

Mechanics:           8*5 "HALF"-Keyboard,
                     COMPTOMETER-Coding = Instant Additions

Functions:           Addition, Subtraction ( as 9-Complement Addition )

Registers:           Input       =  8 Decimals
                     Arithmetic  =  9 Decimals
                     BRDR. CARLSEN
                     Gentofte, Denmark

H O W   T O   U S E   the  CONTEX - B

To CLEAR the REGISTER push the left LEVER down and release it. 

As mentioned to the "Key-Driven-Calculators" BURROUGHS & COMPTOMETER:
Calculator courses suggested to use only the lower-half of the full
keyboard to speed-up additions in saving hand/arm motions:

            instead key 6  press  3 + 3  in sequence
                        7         3 + 4
                        8         4 + 4
                        9         4 + 5

Obviously the method was used, because the lower-half of the keyboard
show more wear on most calculators of this type. Consequently CONTEX
made a "HALF-COMPTOMETER": Smaller, mechanically less sophisticated,
more light-weight and therefore much cheaper than the "big" ones.

Because there are no 9-Complements on the keys, do it in this way ...

A Subtraction Example:                     765 - 432 = 333
  o  Enter on the right columns  "765"

  o  Calculate the SUBTRAHENT MINUS 1        432 - 1 = 431
  o  Calculate the 9-COMPLEMENTS of  "431"           = 568

  o  Hit on the right columns                          5

  o  INSTEAD "Press all 9-Keys left of the subtrahend simultaniously":
     - PRESS all "5"-Keys left of the subtrahend simultaniously
       and than
     - PRESS all "4"-Keys left of the subtrahend simultaniously

For more information:    Have a look at the BURROUGHS site
                         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.  The  CONTEX-A  was an
"open" version and came either in  BAKELITE  or in  PLASTIC  like these:


CONTEX-B  is the "closed" version.  Both adding machines had an unusual
design: Most of the internal levers were made out of pressed fibreboard.

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

© C.HAMANN          09/09/07