Monroe Hand Operated LN User manual

NR CALCULATING MACHINE
OPERATING
INSTRUCTIONS ,$
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OPERATING INSTRUCTIONS
MONROE
CALCULATING MACHINE
Hand Operared LN Models
NR
MONNOE CALCULATING MACHINE COMPANY, INC.
General OIIices, Orqnge, New lersey

Copyright 1953
Monroe Calculating Machine Company, Inc.
Printed in U, S. A.
1045-S
September 19JB

FO R EWO RD
,T1 UtS BOOKLET describes the operating controls
I the Monroe Model LN Calculator and gives step by
tions on the four basic arithmetic functions; addition,
multiplication and division.
and parts o{
step instruc-
subtraction,
The directioos apply to both the 8 and 10 bank LN type Moruoe
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
exacrly the samel the only difference is in their figuring capacities.
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CONTENTS
Description of Operating Controls and Parts
Addition and Subtraction
Multiplicatioo . . .
Division
Decimals
Addition and Subtraction of Decimal Numbers
Multiplication of Decimal Numbers
Division of Decimal Numbers 20
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L2
t4
r6
L7
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MONROE
CALCU LATOR
Model LN
OpercrtinE Controls
1. Upper Dials
2. Lower l)ials
l. farriage Shift Knob
4. Clear-out Crank
!. Operating Crank
6. Repeat and Non Repeat Keys
7. Keyboard Qlear Key
8. Carriage Shift Lever

MONROE MODEL LN
Description of 0peroting Controls ond Ports
l) Upper Diols The set of dials located in the upper parr 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 Diols These are the sixteen (or twenty) dials located in
the lower part of the carriage. The lower dials show the answer in
addition, subraction, and multiplication. They show the renlainder
in division.
3) Corrioge Sh:ft Knob This knob, Iocated at the righr 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.
1l Cleor-out Cronk 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) Operoting Cronk 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 rurn of this crank in order
to follow the instructions in this booklet.

\ 6) Repeot ond Non-repeot Keys When the rePeat key (key marked
\ ,'R,,) is depressed, any figures set on the keyboard remain down until
' cleared by the operator. When the non-rePeat key (key above repeat
key) is depressed, the keyboard clears after each turn of the opera-
ting crank. The repeatkey rnustbe depressed when performing multi'
plication and division.
7l Keyboord Cleor 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) Corrioge Shift Lever By a half turn of this lever, located at the
left front of the machine, the carriage may be shifted to the riSht 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 mast be in upright, or "neutral"
position when clearing.
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ADDITION AND SUBTRACTION
Addition and subtraction can be accomplished with the carriage in
any position but it is suggested that the carriage be placed in posi-
tion 'r1rr, 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.
TO ADD
Depress Non-repeat key. Clear machine.
Set on keyboard
Set on keyboard
Set on keyboard
In lower dials
Make one forward turn of Operating Crank
Make one forward turn of Operating Crank
Make one forward turn of Operating Crank
Total
TO SUBTRACT
Non-repeat key depressed. Clear machine.
Set on keyboard 45 Make one forward turn of Operating Crank
Set on keyboard L5 Make one backward turn of Operating Crank
In lower dials 30 Answer
Repeot key oddition ond subhoclion 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.
L2
23
34
@
Set on keyboard
Change keyboard to read
Chaage keyboard to read
In lower dials
47 Make a forward turn of
Operating Crank
43 Make a forward turn of
Operating Crank
-40 Make a backward turn of
_ Opbrating Crank
50 Answer
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MULT!PLICATION
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 "writingrr'the other figure
in the upper dials with the operating crank. The repeat key must be
depressed when doing multiplication.
Exomple: L2 x 12 = L44
tl{et[od.' Repeat key depressed. Clear machine.
Step 1. With the carriage in position t'1", set 12 on the extreme
right of the keyboard. Turn the Operating Crank forward
2 turns. Note r
Step 2, With the Carriage Shift Lever, shift the carriage one
place to the right. Turn the oPerating Crank forward one
turn.
Resulr.' Upper dials
Keyboard
Lower dials
l2
L2
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.
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 diffetent numbers.
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In the previous example, we multiplied 12 x 12. Suppose we also
had to multiply L2 by )L, and 12 by 15. After completing the first
multiplication, the machine reads as follows: upper dials, 12; key-
board, 12; lower dials, L44.
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.
Exomple: 12x3l=372
12x15=180
Machine reads as stated above.
Clear nothing. Change the 1 in the upper dials to I with
Merhod:
S tep 1. two forward turns of the Operating Crank.
W
Sielt 2, Shift carriage one Place to the iigrt. Ch.tge 2 in the
upper dials to 1 with one backward turn of Operating
Crank.
Result.' Upper dials
Keyboard
Lower dials
Step 3. In a similar manner, change
we have:
Resuh: Upper dials
Keyboard
Lower dials
3I
L2
172 (answer)
the upper dials to 15 and
15
L2
180 (answer)
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 ds the figures on the keyboard and in the
upper dials are correct, the result in the lower dials will be correct.
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Division is just as easy and simple as multiplication. As multipli-
ca{ion is a process of repeated additions, accomPlished by forward
try'ns of the operating crank, so division is a process of continued
ptrbtractions, and is accomplished by backward turns of the opera-
ting crank. The repeat key must be depressed when doing division.
DtvtstoN
Example: L728 + 12 = 144
Merfiod: Repeat key depressed. Clear machine.
Step 1. With the carriage in position ir 1", set the dividend,
L728, 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 riSht 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 aluays 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 tum. (The red 1 in che
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 hrrn.
Result: Lower dials 0 (remainder)
Upper dials L44 (answer)
1{

If the operator is nrrning the crank backward rapidly and goes a
turn or two past the bell, he should simply turn the crank for*ard
until the bell rings, and stop. Listening for these bells makes it
possible to perform the division without watching the machine.
PRACTICE PROBLEMS
1. 510 + 15: 34
2. 1400 + 25 : 56
3. 2432 + 32 : 76
4. L659 + 2r7 : 7
5. L464 + t22 : t2
6. 4810 + L4 : 345
7. 928 +232: 4
8. 1160 + L45 : 8
9. L274 + g8 : 13
10. 510 + 85 : 6
Note: Be srue to clear the "1" from the upper dials
and line up the lower dial figure and keyboard
figure.
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DEC!MALS
On all calculating machines, fractions are expressed as decimals.
For example, L/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 Nlonroe is:
Keyboard decirnal + upper dial decimal = lower dial decimal
Decimol Morkers fhe keyboard decimal is marked by turning one of
the small knurled wheels below the keyboard to the right so that the
yellow decimalmarker appears between the proper keyboardcolumns.
The upper and lower dials decimals are marked by the gray poioters
which can be easily positioned to point off the decimal exactly as
with 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.
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ADDITION AND SUBTRACTION OF DECIMAL N!.'MBERS
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 accornmodate this number of decimal
places. Set the lower dials decimal ar the same number. The upper
dials decimal is at zero (0) and therefore\the Monroe rule, as srared
above holds. I
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Following these instructions, what is the correct decimal setting
for the following problems?
t2.25
3.333
L0.2
25.783
The correct decimal setting is:
152.45
160.0
- 7 5.242
237.208
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-
tractionrgiven on page 11, the result will always be correct.
PRACTICE PROBLEMS
13.00
36.60
- 44.30
26.26
3t.35
42.50
r.46
23.r9
- 3.46
r.56
-2t.20
3r.45
t7
31.56 98.90 12.3t

MULTIPLICATION OF DECIMAL NUMBERS
tlandling 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 t-d<:commodate the
other number. Then, following the Monroe rule for deiimals, add the
number of decimal places on rhe keyboard to the number of decimal
places in the upper dials and ser rhe 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 aecimal 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?
2A.L25x.425=8.553125
The larger number (20.L2) will be set on the keyboard. It has three
decimaL places so the keyboard decimal marker should be set at 3'
Theother number (.42il will be entered in the upper dial, so set the
upper dials decimal at 3. Add the two (1 + ) = 6) and set the lower
.li.l, deci*^l at 6. Set the decimal markers accordingly and do the
example following the steP by step instructions below'
Metfiod: UpPer dials decimal 3
Keyboard decimal 3
Lower dials decimal 6Repeat key dePressed
Step 1, Set 20.L25 on the keyboard (20 to the left of the key-
board decimal marker and .L25 to the right)'
Step 2. V/ith the cariage in position "1", rurn 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.
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Result.' Upper dials
Lower dials .425
8.553L25 Answer
Note that the .425 appears in the upper dial to the right
J 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 largesr 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 ro 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 rwo. Enter all
figures around these pre-set decimals and tbe results will all be
correct. The following example illustrates this.
24.75 x .35= 8.6625
12.5 x .24= 7.8
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 1
Lower dials 5
Try the above problems and check the given answers to see if you
are correct.
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DIYISION 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 ooe more place than this (to permit rounding off)' 4gain, for the
lower dials decimal, add the keyboard and upper dials decimal and
set the lower dials decimal at this number'
Exomple: 22.868+ 6-7 = 3.413 (rounded off)
12.33 + 4.25 = 2.90L (rounded off)
5.56 + .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+L=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.
lilerftod: Upper dials
Keyboard
Lower dials
4-
3 RePeat key dePressed
7
Step 1, 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 atign the left hand digit in the lower
dials with the Ieft hand digit on the keyboard)'
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