How to operate the Dalton Adding Machine

The Dalton Adding Machine can add, but also subtract, multiply and more. How to operate it is not always immediately obvious today from just looking at the machine. Below will show how to do some of these operations on a Dalton.

The machine used here is a very basic Super Series machine, i.e. a 2nd generation Dalton 10-key adding machine as was introduced in 1921. The pre-1921 first-generation Dalton machines however work much the same way, just that some function keys are in different locations. Early machines also have slightly different method of e.g. how to perform a total or sub-total. 

More advanced Super Series machines have more features and are capable of more functions:

Note by the way that the paper should be mounted to feed from the bottom of the roll.

Clearing the machine

Before any operation, make sure the machine is clear, i.e. is at zero. This is done by doing a total; press-in the total-key, it will latch in the pressed-in position. Then pull the lever forward all the way and let it return. An asterisk printed on the paper tape will confirm that the machine is empty at the start of a calculation. (Or will print a value if the machine was not empty, of course.)

If the total-key is blocked, first do an "empty-stroke". That is, one stroke of the lever with an 'empty' keyboard. This will enable the total-key. The keyboard-clear indicator is the oblong window just behind the digit-keys; if this shows 'blank' (no dots) then the keyboard is 'empty'. A total or sub-total always has to be preceded by an empty-stroke.

(Apart from the keyboard-clear indicator, control-keys on the Dalton are helpfully labeled with their function.)

Adding

To then start an addition, enter every value as is done on a modern calculator; so $ 12.50 is entered as 1, 2, 5 and 0 in that order. The keyboard-clear indicator will show the number of digits entered with coloured dots. 

To add this value into the register (or accumulator) of the machine, pull the lever forward all the way and let it return. 

Repeat for every value to be added. The keyboard will be cleared automatically at the end of a stroke.

To get the total, first do one empty stroke, i.e. a pull of the lever without any number entered (the keyboard-clear indicator blank). Then push in the total-key and do a stroke. The total will print with an asterisk next to it and the machine register is cleared to zero. (On most Dalton machines, the totals are printed in red. This most-basic machine however does not have the bi-color function.) 

The total sum of the values 12.50, 37.97 and 6.95 is thus printed as 57.42 on the paper. (This machine has a wider space between the 2nd and 3rd column numbers to make reading of dollar and cent values easier - this can however vary per machine.)

A sub-total prints the value of the register with an 'S' in the right margin, but does not re-set the register to zero. Example below with a sub-total after adding 123, 456 and 789, and then a total after adding 321, 654 and 987. 

Above shown on a bi-color capable machine, with the total and sub-total lines printed in red.

When e.g. the total-key or another function key is pressed in error, pressing the release-key will release it.

Pressing down the large correction-key will completely clear the keyboard entry. Pressing the backspace-key will remove one, right-most digit.

Multiplying (from right)

Supposing a 21% surcharge (VAT, carriage, etc) needs to be added to the $ 57.42 value calculated above. Then 57.42 needs to be multiplied by 1.21. 

Enter 5742 on the keyboard and push down and to the back the multiply-key to latch it in the down-position. (The multiply-key prevents the keyboard being cleared at the end of a stroke. That is all it does.) 

With one lever-stroke enter the right-most digit of 121. Then enter a zero on the keyboard, this will change the number entered to 57420, and pull the lever twice to enter the next digit of 121. Add another zero (making 574200) and one stroke to enter third digit of 121.

Then press the multiply-key once to release it, press down the correction-key to empty the keyboard and do an empty-stroke followed by a taking a total.

To point-off: the multiplicand and multiplier both have 2 decimals, so the result will have 2+2 is 4 decimals. The result of 694782 should thus be read as 69.4782. This gives that $ 57.42 with a 21% surcharge added as $ 69.48 when rounded to dollars and cents.

Dividing (multiplication from left)

On the Dalton, dividing is done by multiplication with the reciprocal of the divisor. I.e. dividing by 5 would be a multiplication by 0.2 (1/5). A table of reciprocals was provided with the machine, a larger table of reciprocals was available separately from the company for numbers of 1 to 10,000. 

Supposing the amount of $ 69.48 needs to be paid in 12 instalments, the value needs to be divided by 12. Looking this up in the table, the reciprocal of 12 is 0.083333.

To multiply 69.48 with 0.083333, the value of 6948 is entered and padded with zeroes to fill the buffer. Then the backspace-key is pressed once. I.e. on an 8-column machine, the keyboard-clear indicator will show 7 digits are entered.

Then multiply from the left, so start with 8 strokes of the lever for the left-most digit. Press the backspace-key once and enter the next digit with 3 strokes. Repeat until the keyboard is empty, or enough digits for the precision needed have been done (e.g. 5 digits to get a fair 4-digit answer).

Then draw the total - showing the answer as 57899973. The answer is approached from below with this method, so rounding should be up. The answer is then $ 5.79 when rounded to two decimals for dollars and cents.

Doing a quick multiplication by 12 of 579 from the right gives 6948 confirming this is the exact, correct answer. (Otherwise, there would be a correction for the final instalment to make up for any fractional mismatch.)

Subtracting

On a basic Dalton with 9-complement subtraction, digit-keys also have red numbers (co-digits). Some of the more advanced (expensive!) Daltons have direct-subtraction. These machines do not have red co-digits and can do subtraction directly with a number entered the usual way on the keyboard.

For a Dalton with red co-digits; to subtract $ 67.59 from $ 128.95 first enter 12895 in the machine. To create a record of what the operator meant to do, enter 6759 and depress the non-add key and pull the lever. This prints the number with a little arrow to its right; the number is only printed and not added to the machine's total.

Then enter 6759 again, but now using the red digits! Depress the subtract-key and pull the lever. The machine cannot print a number that is entered with red digits, but will only print a minus-sign in the right margin. Then draw a total.

This shows $ 61.36 as the result. 

Note that with this 9-complement method of subtraction on the Dalton, the paper does not have proof of the number that the machine subtracted.

Adding compound numbers

To add compound numbers, such as feet and inches, pounds and ounces or hours and minutes, these are entered in their own columns.

To calculate e.g. the total time taken for a job from submitted hour cards, the times are added with the hour values separated from the minutes with zeroes. I.e. a value of 3:45 is entered as 300045. 

After adding the times of 3:45, 4:10, 2:55, 8:05 and 7:40 in this manner, a sub-total is printed.

This sub-total shows the sum of the minutes to be 155. With 60 minutes in an hour, it can be seen at a glance that two hours (120 minutes) need to be taken off, 155 being between 120 (2*60) and 180 (3*60). Enter on the keyboard 99940. (99940 is actually minus 60 in complementary notation, for a 5-digit register.) Then pull the lever twice to take off 60 twice from the minutes column. The overflow of every 'subtraction' of 60 at the same time adds one to the hours value. Then print the total.

The total now shows the sum of the entered time-values is 26 hours and 35 minutes.

The split-feature of more advanced Daltons can be used to prevent printing of the zeroes between the hours and minutes, showing the values in clearly separate columns - more readable.

The same method of course works for feet and inches (use 99988, i.e. minus 12) or pounds and ounces (99984).

There is more...

The above are pretty much the basics of operating a Daltong Adding Machine. There are more shortcuts and tricks for the Dalton, but many are actually not specific to the Dalton and will work for any 10-key adding machine. 

The company gave examples on e.g. how to quickly calculate a 4% discount on a bill, how to check an extended invoice or a recommended way to do a trial balance with both credit and debit values. 

The Dalton company also provided more advanced calculating techniques, such as how to do a multiplication where the answer is larger than the capacity of the machine - e.g. how to calculate a 12 digit result on an 8-column machine.

Class in mechanical accounting and touch-adding, New York University Summer School

Understandable then that in their day, the operation and use of the Dalton Adding Machine was taught in (business) schools.

(That will have been a very noisy classroom, with 20+ Dalton machines in action!)