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CONTEX - B
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
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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
Manufacturer:
BRDR. CARLSEN
Gentofte, Denmark
1960
H O W T O U S E the CONTEX - B
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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
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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
3+3
4+4
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 :
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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:
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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