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```MpNROE CALCULATING MACHINE

MODELS

Hand Operated

LN

OPERATING INSTRUCTIONS

MONROE

CALCULATING MACHINE

Hand Operated LN Models

MpNROE

MONROE CALCULATING MACHINE COMPANY. INC.

Generol Offices, Orange, New Jersey

Monroe Calculating Machine Company, Inc.

Printed in U. S. A.
1045-S

September 1958

FOREWORD

T HIS BOOKLET describes the operating controls and parts of
the Monroe Model LN Calculator and gives step by step instruc¬
tions on the four basic arithmetic functions; addition, subtraction,
multiplication and division.

The directions apply to both the 8 and 10 bank LN type Monroe
hand operated machines. The former model has an eight column key¬
board, eight places in the upper dials, and sixteen places in the
lower or result dials. The latter, Model LN 200, is equipped with a
ten column keyboard, ten places in the upper dials, and twenty places
in the lower dials. The actual operation of these two models is
exactly the same; the only difference is in their figuring capacities.

CONTENTS

Description of Operating Controls and Parts . 9

Addition and Subtraction. 11

Multiplication. 12

Division. 14

Decimals . 16

Addition and Subtraction of Decimal Numbers. 17

Multiplication of Decimal Numbers. 18

Division of Decimal Numbers. 20

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MONROE

CALCULATOR
Model LN

Operating Controls

1. Upper Dials

2. Lower Dials

3- Carriage Shift Knob
4. Clear-out Crank

5 . Operating Crank

6. Repeat and Non Repeat Keys

7. Keyboard Clear Key

8. Carriage Shift Lever

8

MONROE MODEL LN

Description of Operating Controls ond Parts

1) Upper Dials The set of dials located in the upper part of the
moveable carriage is called the upper dials. These dials show the
quotient (answer) of a division problem in red figures. In multi¬
plication, they show the multiplier (number by which you multiply)
in black figures.

2) Lower Dials These are the sixteen (or twenty) dials located in
the lower part of the carriage. The lower dials show the answer in
addition, subtraction, and multiplication. They show the remainder
in division.

3) Carriage Shift Knob This knob, located at the right end of the
carriage, is for shifting several places at a time. Simply lift up on
the knob and slide the carriage to the desired position.

4) Clear-out Crank This is the smaller crank located at the right
end of the carriage. A forward (clockwise) turn clears the upper
dials, and a backward (counter-clockwise) turn clears the lower
dials.

5) Operating Crank The operating crank is the larger crank located
on the right side of the machine. This crank is used in all opera¬
tions on the machine. The operator should clearly understand what
is meant by a forward turn and a backward turn of this crank in order
to follow the instructions in this booklet.

9

6) Repeat and Non-repeat Keys When the repeat key (key marked
"R") is depressed, any figures set on the keyboard remain down until
cleared by the operator. W'hen the non-repeat key (key above repeat
key) is depressed, the keyboard clears after each turn of the opera¬
ting crank. The repeat key mus/be depressed when performing multi¬
plication and division.

7) Keyboard Clear Key The keyboard keys are cleared in one of
two ways, either by depressing the large square zero clear button,
which clears the entire keyboard; or by depressing the individual
"zero" clear keys at the bottom of each column, which clear keys one
at a time.

8) Carriage Shift Lever By a half turn of this lever, located at the
left front of the machine, the carriage may be shifted to the right or
left as desired. The operating crank must be in upright, or "neutral"
position when shifting.

TO CLEAR THE MONROE MODEL LN

The operator should always remember to clear the entire machine
before starting any new work. Complete machine clearance is a
simple procedure which can be done almost subconsciously.

To clear keyboard — Depress Keyboard Clear Key

To clear upper dials - Make a complete forward turn of
Clear-out Crank

To clear lower dials - Make a complete backward turn of
Clear-out Crank

NOTE: The operating crank must be in upright, or "neutral"
position when clearing.

10

Addition and subtraction can be accomplished with the carriage in
any position but it is suggested that the carriage be placed in posi¬
tion "1", that is, as far to the left as possible.

The most rapid and efficient way to add and subtract is with the
non-repeat key depressed so the numbers automatically clear from
the keyboard.

Depress Non-repeat key. Clear machine.

Set on keyboard
Set on keyboard
Set on keyboard
In lower dials

12 Make one
23 Make one
34 Make one
69 Total

forward turn of
forward turn of
forward turn of

Operating Crank
Operating Crank
Operating Crank

TO SUBTRACT

Non-repeat key depressed. Clear machine.

Set on keyboard 45 Make one forward turn of Operating Crank
Set on keyboard 15 Make one backward turn of Operating Crank
In lower dials 30 Answer

Repeat key addition and subtraction Addition and subtraction can
be done exactly as above with the repeat key depressed. When this
is done, the number added or subtracted remains on the keyboard
after the turn of the operating crank. This saves time when adding
and subtracting numbers which have one or more digits the same.
Try it with the following example:

Depress Repeat key. Clear machine.

Set on keyboard

47

Make a forward turn of
Operating Crank

Change keyboard to read

43

Make a forward turn of
Operating Crank

Change keyboard to read

-40

Make a backward turn of
Operating Crank

In lower dials

"50"

11

MULTIPLICATION

Multiplication is a series of additions and is a simple process on
the Monroe Model LN . It is accomplished by setting one figure
(usually the larger) on the keyboard and "writing" the other figure
in the upper dials with the operating crank. The repeat key must be
depressed when doing multiplication.

Example: 12 x 12 “ 144

Method: Repeat key depressed. Clear machine.

Step 1. With the carriage in position "1", set 12 on the extreme
right of the keyboard. Turn the Operating Crank forward
2 turns. Note •

Step 2. With the Carriage Shift Lever, shift the carriage one
place to the right. Turn the operating Crank forward one
turn.

Result: Upper dials 12

Keyboard 12

Lower dials 144 (answer)

This gives a complete and positive check of accuracy. If the correct
numbers show in the upper dials and keyboard, the answer cannot
be incorrect.

• If too large a number is turned into one of the upper dials, it can

easily be corrected. Simply position the carriage so the carriage
position arrow points to the incorrect dial and turn the operating
crank backward until the correct number appears. If the incorrect
number is too small, turn the crank forward until it is correct. i

CONSTANT MULTIPLIER

The above explanation of correcting the upper dials naturally leads
to the problem where we have to multiply the same number by sev¬
eral different numbers.

12

In the previous example, we multiplied 12 x 12. Suppose we also
had to multiply 12 by 31, and 12 by 15. After completing the first
multiplication, the machine reads as follows: upper dials, 12; key¬
board, 12; lower dials, 144.

It is not necessary to clear the machine. Leave the 12 on the key¬
board and simply change the upper dials to the next multiplier.

Example: 12 x 31 “ 372

12 x 15 - 180

Method: Machine reads as stated above.

Step 1. Clear nothing. Change the 1 in the upper dials to 3 with
two forward turns of the Operating Crank.

V . .

Step 2. Shift carriage one place to the r+ght. Change 2 in the
upper dials to 1 with one backward turn of Operating
Crank.

Result: Upper dials
Keyboard
Lower dials

31

12

Step 3. In a similar manner, change the upper dials to 15 and
we have:

Result: Upper dials
Keyboard
Lower dials

15

12

This entire operation is extremely simple. It requires no expert
knowledge, skill or training, and you know your result is absolutely
accurate because all the figures used are visible in the machine.

It can be seen from the above that multiplication can be done in
either direction. As long as the figures on the keyboard and in the
upper dials are correct, the result in the lower dials will be correct.

13

DIVISION

Division is just as easy and simple as multiplication. As multipli¬
cation is a process of repeated additions, accomplished by forward
turns of the operating crank, so division is a process of continued
subtractions, and is accomplished by backward turns of the opera¬
ting crank. The repeat key must be depressed when doing division.

Example: 1728 * 12 “ 144

Method: Repeat key depressed. Clear machine.

Step I. With the carriage in position "1", set the dividend,
1728, on the extreme right of the keyboard. Make one
forward turn of the Operating Crank. Depress the Key¬
board Clear Key and turn Clear-out Crank clockwise.
(This clears the keyboard and clears the "1" out of the
upper dials.)

Step 2. Set the divisor, 12, on the right of the keyboard and
move the carriage two spaces to the right so that the
divisor, 12, is in direct alignment with 17, the first
two figures of the dividend in the lower dials.

NOTE: In division problems, the left hand figure of the
divisor on the keyboard must always be either
directly under the left hand figure of the divi¬
dend in the lower dials, or beyond it to the left.

Step 3. Turn the Operating Crank backward until the bell rings.

Turn the Crank forward one turn. (The red 1 in the
upper dials is the first digit of the answer.) Shift the
carriage one place to the left. Turn the Crank backward
until the bell rings. Turn the Crank forward one turn
(bell also rings on the one forward turn to warn you not
to go any farther).

Step 4. Continue this operation of shifting the carriage one
place to the left, turning the Crank back until the bell
rings and turning the Crank forward one turn.

Result: Lower dials 0 (remainder)

Upper dials 144 (answer)

14

If the operator is turning the crank backward rapidly and goes a
turn or two past the bell, he should simply turn the crank forward
until the bell tings, and stop. Listening for these bells makes it
possible to perform the division without watching the machine.

PRACTICE PROBLEMS

1 .

510

-5- 15

—

34

2.

1400

-5- 25

=

56

3.

2432

+ 32

=

76

4.

1659

-5- 237

=

7

5.

1464

-5- 122

=

12

6.

4830

-5- 14

=

345

7.

928

-5- 232

=

4

8.

1160

* 145

=

8

9.

1274

* 98

-

13

10.

510

-5- 85

-

6

Note: Be sure to clear the "1” from the upper dials
and line up the lower dial figure and keyboard
figure.

15

DECIMALS

\

On all calculating machines, fractions are expressed as decimals.
For example, 1/4 = .25, 5/8 ■ .625, etc.

The arrangement of the dials and the keyboard on the Monroe
makes it particularly adaptable to handling calculations involving
decimal numbers.

On the Monroe , all decimals can be set for a complete group of
problems before starting the work, and all the calculations can be
completed without any resetting of the decimals. The work is done
entirely around pre-set, fixed decimals. The one simple rule for
setting decimals on the Monroe is:

Keyboard decimal + upper dial decimal “ lower dial decimal

Decimal Markers The keyboard decimal is marked by turning one of
the small knurled wheels below the keyboard to the right so that the
yellow decimal marker appears between the proper keyboard columns.

The upper and lower dials decimals are marked by the gray pointers
which can be easily positioned to point off the decimal exactly as
w r ith paper and pencil. To set a decimal at 2 in the dials, simply
set the marker to the left of the 2 on the slide.

16

ADDITION AND SUBTRACTION OF DECIMAL NUMBERS

To pre-set the decimals for a group of problems involving addition
and subtraction, examine the numbers in all the problems and de¬
termine which has the largest number of decimal places. Set the
keyboard decimal marker to accommodate this number of decimal
places. Set the lower dials decimal at the same number. The upper
dials decimal is at zero (0) and therefore the Monroe rule, as stated
above holds.

Following these instructions, what is the correct decimal setting
for the following problems?

12.25
3.333
10.2
25.783

The correct decimal setting is:

Upper dials 0

Keyboard 3

Lower dials 3

because 3 is the greatest number of decimal places which appears
in these figures.

Set these numbers on the keyboard exactly as they are written. The
figures which appear to the left of the decimal point should be set
to the left of the keyboard decimal marker, and those which appear
to the right of the decimal should be set to the right of the keyboard
decimal marker. Following the instructions for addition and sub¬
traction, given on page 11, the result will always be correct.

PRACTICE PROBLEMS

152.45
160.0
- 75.242
237.208

13.00

36.60

-44.30

26.26

31.56

31.35

42.50

1.46

23.59

98.90

-3.46

1.56

- 21.20

35.45

12.35

17

MULTIPLICATION OF DECIMAL NUMBERS

Handling decimal numbers in multiplication is also very simple. As
you remember from the previous instructions, to multiply on the
Monroe Model LN, you set the larger number on the keyboard and,
with the operating crank, turn the other number into the upper dials.
When this is done, the answer appears in the lower dials.

Therefore, when multiplying decimal numbers, you should set the
keyboard decimal marker to accommodate the largest number in the
problem and the upper dials decimal marker to accommodate the
other number. Then, following the Monroe rule for decimals, add the
number of decimal places on the keyboard to the number of decimal
places in the upper dials and set the lower dials decimal marker at
this number of decimal places. This is exactly how you point off
the decimal when multiplying by pencil and paper - add the number
of decimal places in the two numbers and point off this many places
in the result. All decimal markers should be set before beginning
any of the work.

What is the correct decimal setting for the following example?

20.125 x .425 - 8.553125

The larger number (20.125) will be set on the keyboard. It has three
decimal places so the keyboard decimal marker should be set at 3*
The other number (.425) will be entered in the upper dial, so set the
upper dials decimal at 3. Add the two (3 + 3 = 6) and set the lower
dials decimal at 6. Set the decimal markers accordingly and do the
example following the step by step instructions below.

Method: Upper dials decimal 3

Keyboard decimal 3 Repeat key depressed

Lower dials decimal 6

Step 1. Set 20.125 on the keyboard (20 to the left of the key¬
board decimal marker and .125 to the right).

Step 2. With the carriage in position "1", turn the Operating
Crank 5 turns forward. Shift the carriage one place to
the right. Make 2 forward turns. Shift the carriage to the
right. Make 4 forward turns.

18

Result: Upper dials
Lower dials

.425

Note that the .425 appears in the upper dial to the right
of the decimal marker and the lower dials decimal
marker correctly points off the answer.

We should always set the decimal for a whole group of problems to
avoid changing the decimal markers for every problem. To do this
for a group of multiplication problems, simply find the largest num¬
ber of decimal places appearing in the numbers to be set on the
keyboard. Set the keyboard decimal marker for this number. Find the
largest number of decimal places to be entered in the upper dials.
Set the upper dial decimal for this number. Follow the Monroe rule
and set the lower dials decimal at the sum of these two. Enter all
figures around these pre-set decimals and the results will all be
correct. The following example illustrates this.

24.75 x .35 - 8.6625

32.5 x .24 - 7.8

110.333 x 1.4 - 154.4662

The largest number of decimal places in the numbers which go on
the keyboard is 3; in numbers which go in the upper dials is 2, and
therefore, the decimal setting should be:

Upper dials 2

Keyboard 3

Lower dials 5

Try the above problems and check the given answers to see if you
are correct.

19

DIVISION OF DECIMAL NUMBERS

In division, as explained in the instructions for simple division,
both numbers, (dividend and divisor) are set on the keyboard. There¬
fore, when working with decimal numbers, we simply examine all
the numbers to find the largest number of decimal places appearing
in the whole group of problems at hand,. Set the keyboard decimal at
this number. To set the upper dials decimal always decide how many
decimal places are required in the answer and set the decimal marker
to one more place than this (to permit rounding off). Again, for the
lower dials decimal, add the keyboard and upper dials decimal and
set the lower dials decimal at this number.

Example: 22.868 v 6.7 ** 3*413 (rounded off)

12.33 -r 4.25 = 2.901 (rounded off)

5.56 -r .66 *= 8.424 (rounded off)

Three is the greatest number of decimal places appearing in all the
numbers in this group of problems. Set the keyboard decimal at 3.
We require 3 decimal places in the answers, so set the upper dials
decimal at 4 (3 + 1 =4). Then the lower dials decimal is 7 (3 + 4 =7).
Step by step instructions for the first problem follows. Try the last
two by yourself.

Method: Upper dials 4

Keyboard 3 Repeat key depressed

Lower dials

Step I. Set 22.868 on the keyboard. Shift the carriage so the
lower dial decimal at 7 is in direct alignment with the
keyboard decimal at 3- Turn the Operating Crank for¬
ward one turn. Make one forward turn of the Clear-out
Crank to clear 1 from the upper dials. Depress the
Keyboard Clear Key.

Step 2. Set 6.7 on the keyboard. Shift the carriage one place to
the right. (To align the left hand digit in the lower
dials with the left hand digit on the keyboard).

20

Step j. Turn the Operating Crank backward until the bell rings.

Make one forward turn. Shift the carriage one place to
the left.

Step 4. Continue as in Step 3 until the carriage reaches the
first position.

Result: Upper dials 3.4131 (or 3.413 rounded off)

Do the last two problems and check the answers above for accuracy.

PRACTICE PROBLEMS

Results are rounded off to two (2) decimal places.

1.

128.43

-5- 29.5

= 4.35

2.

962.99

-5- 37.3

= 25.82

3.

26.938

+ 2.45

= 11.00

4.

63.824

-5- 5.75

= 11.10

5.

16.50

-5- .573

= 28.80

Note: Be sure to line up the lower dials deci¬
mal with the keyboard decimal before setting
the first number in the lower dials.

21

MpNROE

® &

' /calculating

'ACCOUNTING
'DATA processing

m^nr<3e

{ s/

To find the Square Hoot of a number using
the Monroe Calculating Machine.

Take the number 3.03 as an example.

0

Take out odd numbers from under the first (far left hand) 3 in the
above number, until the figure 3 is reached (i.e. 1, 3 etc.) this is
too high, so wind back to previous figure and press the next key
below the figure 3 i.e. the figure 2 in this case and move the
carriage to the left one digit and press the odd number key in the
next row to the right until the figure 9 i3 reached i.e. 21, 23, 25,
27 , and the number 29 is read. Fow instead of the figure 2

press down figure 3 and instead of the figure 9, press down the
figure 1 thus giving the number 31 on the keyboard and then continue
to take out odd numbers in the right hand line of keys, thus 33, 35,
now 35 is too high so wind back on the handle to the last figure //w
the top window which in this case is 1.7, press the key No.4 instead
of 5 also pressing the key Fo.1 in the next right hand column, and
move the carriage to the left one digit thus the number 341 appears
on the keyboard and continue to press down the odd number; keys on the
right hand column thus 343, 345, 347, until the number 349 is reached
this is too high, so come back to 348 press down the key Fo.1 on
the next right hand column thus giving 3481 on the keyboard, move
the carriage another digit to the left now 1.74 is in red figures in
the top window, now 3481 on the keyboard is too high, so come back
to 3480 move up one more digit to the left on the carriage and take
out odd numbers in the next right hand column. Thus giving 34801,
34803, 34805, 34807, 34-809 continue to take out odd numbers thus
34811, 34813, which is too high,come back to 34812 move carriage to
left one digit and in the top window the number 1.74-06 should appear.
In the next available right hand column press down the odd number
keys thus giving 348121, 348123, 348125, 348127, 348129, 348131,
348133, 34-8135, 34-8137, this last number is too high, so come back
to 348136 and the number 1.74068 in Red in the top window. Move
the carriage to the left one more digit continue to take out odd
numbers in the next right hand column thus giving 3481361, 3481363,
3481395, 3481367, 34-81369, 3^81371, 3481373, 3481375, 3481377,

3481379 the last figure here is too high, so wind back one, giving
the answer to 3*03^ as 1.740689.

NCI TEL: - P\LL NC=> OPERATIONS f\R£. ThT

-Sfl/vl EL FOR D/I//J/QA/

``` 