Details:

While competitors use the amount of displacement determined by an input module, this machine uses speed to transfer key-input to the accumulator. To do so keys in each column are connected to a kind of gearbox with 9 speeds. If a “1” is pushed, the lowest gear is activated, if a “2” is pushed, the second gear is activated and so on. When a calculation operation is activated (e.g. “+”) the machine makes a rotation to transfer the selected digits from all columns into the accumulator.

While this is an analogue operation, a smart construction properly digitises the results at the end of the operation.

It’s advertised as a “Silent speed mechanism”. The fact that the actual calculation process is analogue allows for continuous rotation when adding/subtracting for multiplication and division. It makes the machine fast enough to directly input the multiplier one digit after the other while the machine is calculating. As a result there is no need for a multiplication register.

Furthermore, while dividing there is a smart detection system to predict wether a next subtraction will end with a negative result. In that case the next division does not take place. In stead the carriage is moved to the next position. Doing so saves an unnecessary subtraction as well as a the related corrective addition. The silent speed mechanism + the prediction mechanism are the reasons why in particular a division is executed much faster than on competitive machines.

Compared to the 10EFA, the 8CMR is a simpler and much cheaper calculator. Internally it is highly similar to the 8ADX. With its more modern look it obviously is a later model. While the 8CM, 8CMA and 8CMF are mentioned in other sources, I didn’t find any reference to the CMR.

Usage:

Addition/subtraction:

Enter a number and hit the “+” or the “-” key.

Multiplication:

Enter the first number in the main input field. Enter the second number in the rightmost column. Multiplication is immediately executed per entered digit.

Division

Put the switch next to the “9” in the “+” position. Enter the first number and hit the “+ DIVIDEND” key. Enter the second number and hit the “:” key. The division is now executed. The result appears in the upper register.

Function of some keys, switches etc

- The keys “UPPER DIAL” and “MIDDLE DIAL” reset the registers on the carriage.
- The key “KEYBOARD” resets the keyboard.
- The 8 buttons below the counter register are tab settings. On “CARR RIGHT” or “CARR LEFT” the carriage travels until the desired tab position. It is used to limit the number of digits in the result of a division.
- The key “CARRIAGE RETURN” brings the carriage to its most left position.
- The position of the switch next to the “9” of the multiplier column determines whether the counter adds or subtracts.
- The switch between the “+” and “X” key determines whether after division the carriage returns to its initial position (white) or not (blue) .

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Serial number:

Build in:

Functions:

Rotation speed:

Market-introduction:

Production until:

Price:

685544

?

Addition, Subtraction, Fully automatic Multiplication and Fully automatic Division

1300 additions or subtractions per min.

1963

1967

Ca. DM. 3390 in 1963 (for the 8CM version, Source: Büromaschinen Lexikon)

Slow motion

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