CONTEX - 20

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 *********************************************************************** ( 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 |

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: *********************************************************************** © C.HAMANN http://public.BHT-Berlin.de/hamann 03/25/08 |