Details:

While competitors use the amount of displacement determined by an input module to transfer key-input to the accumulator,  this machine uses speed to transfer the entered digit. 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 whether a next subtraction will end with a negative result.  In that case the next division does not take place.  Instead 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.

The EFA is a top model. Except for the SKA this 10-digit  EFA models belong to the most expensive Marchants in 1958.
There are different versions. E.g. one with back transfer.

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. The order of input (high to low or low to high digit) of the multiplier can be chosen with the top-right sliding switch.

Division          

Enter the first number and hit the “+” key.  Enter the second number and hit the “:” key. The division is now executed. The result appears in the upper register.

Depending on the position of the switch between the “+” and “X” key determines whether the remainder stays in the accumulator or wether it is reset to 0.

Pushing the “line-up” key together with the “:” key results in carriage return to its starting position after performing a division.  That way it is immediately ready for the next division.

Function of some keys, switches etc

• The keys “upper dial” and “middle dial”  reset the registers on the carriage.
• The key “lock or clear” has two different functions. It normally resets the keyboard. If it is pressed while pushing number keys, these keys will not be reset after a calculation.  To unlock the keyboard push the “unlock” key.  
• The bottom row 10 to 1 are tab settings.  For “1” and “10” the carriage immediately moves to the set position. The other positions require the “TAB” key to be pushed
• The position of the grey switch next to the rightmost “9” determines whether the counter adds or subtracts.

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Serial number:

Built in:

Functions:

Rotation speed:

Market-introduction:

Production until:

Price:

562263

1956/1957

Addition, Subtraction, Fully automatic  Multiplication and  Fully automatic Division

1300 additions or subtractions per min.

1950

1962

Approx. DM. 5640  in 1958     (Source: Büromaschinen Lexikon)