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FACIT   CM2-16

Have a look inside

T E C H N I C A L   D A T A   of the Mechanical Calculator   FACIT CM2-16

Serial Number(s):    1003640 (=Label outside)  753793 (=Engraving inside)

Dimensions:   (ca.)  Width   =  13_1/2" /  34 cm
                     Depth   =  11    " /  28 cm
                     Height  =   6_1/4" /  16 cm

Weight:       (ca.)  17_1/2 lbs  /  8 kg

Mechanics:           10-Block-Keyboard
                     Serial-to-parallel conversion with
                     Pin-Wheel / Sprossenrad

Functions:           Add, Subtract, Multiply, Divide
                     Double Back-Transfer / Doppel-Rueckuebertragung

Registers:             I  Input       =  11 Decimals
                      II  Counter     =   9 Decimals
                     III  Arithmetic  =  16 Decimals

H O W   T O   U S E    the  FACIT CM2-16


(A) Crank:
For addition (+) the crank is turned clockwise; for subtraction (-) the
crank is turned counter-clockwise. In the idle position the crank is DOWN
& LOCKED. To make one or more turns with the crank, pull out the handle to
unlock. When finished the turn(s), let the handle snap into lock again. The
locked down position only makes other functions (ex. clearing) accessible.

REMARK:      Every started turn has to be finished completely!
             Accidentally started turns are correctible somehow.

(B) Clearing Arithmetic Unit, Counter & Input:
On the left side the LEVER-PAIR is for clearing registers (III)&(II) by
pressing down the left or right lever (or both). The LEVER on the right
side will clear and reset the input unit (I) by pushing it backward (with
thumb on lever and index finger on crank axle).

REMARK:      Prior to each task, reg.(I),(II)&(III) have to be cleared.

(C) Shifting the Input Unit with the Entered Number:
Left of the number keys, the RED KEY-PAIR let the input unit STEP left
[<-] or right [->]. The actual position is marked with a (white) DOT
above the counter. Right of the 10-Block keys, the RED [<16] KEY and the
RED [<11] KEY let the input unit JUMP to the left positions. With the
[<11] KEY the counter stays in 1st position; with the [<16] KEY the
counter jumps to 8th position. In both cases the input unit will be
filled up with zeros.

(D) Counting Direction:
After clearing the counter unit (II), it depends of the first crank turn
(clockwise or counter-clockwise), that the counter will go either (+) or
(-). In case of (+) the counter & arithmetic unit are working in the
same; in case of (-) both are working in opposite direction. This is
shown with a RED INDICATOR at the left of the counter unit.

(E) Back Transfer:
The single handle on the left side is the TRANSFER LEVER. Pulling it down
will (depending where the input unit is located):
(A) Transfer a result from the arithmetic unit (III) into input unit (I):
    Push [<11] KEY to bring unit (I) under unit (III).
(B) Transfer a quotient from the counter (II) into input unit (I):
    Bring unit (I) in START-Position!
The former content of the input unit (I) will be overwritten and the
registers (III) & (II) are cleared. Transfers are useful for continuous
multiplications or shifting a sequence of figures from an interim result.

REMARK:      Is the content of register (III) bigger than register (I),
             ONLY THE FRACTION opposit to reg.(I) will be transfered!

Example:     123 + 45 - 6  =  162

ADD: Enter the first number (123) into input unit. Make a positive
(clockwise) turn with the crank to transfer the number into arithmetic
unit. The counting unit displays the figure 1. Clear the input unit.
Enter the second number (45). Make a positive (clockwise) turn with the
crank to add the number. The arithmetic unit displays the intermediate
sum (168) and the counting unit displays the figure 2.

SUBTRACT: Clear the input unit. Enter the third number (6). Make a
negative (counter-clockwise) turn with the crank. The arithmetic unit
displays the result (162) and the counting unit is decreased by 1.

REMARK:      NEGATIVE RESULTS are displayed in the arithmetic unit
             as the COMPLEMENT of the next higher 10, 100, 1000, ...

             Example:   -12  =  99...9988

REMARK:      The POSITIVE VALUE can be derived in 2 steps:
             (A) BACK TRANSFER from reg.(III) into reg.(I)
             (B) One NEGATIVE TURN with the crank...

             Example:        =  99...0012

Example:     123 x 45  =  5535

Enter the multiplicand (123) into input unit. Make positive (clockwise)
turns with the crank, until the second figure of the multiplicator (5)
will appear in the 1st position of the counter unit. Move the input unit
with the STEP [<-] key to position 2. Repeat making positive turns with
the crank, until the first figure of the multiplicator (4) appears in the
2nd position of the counter unit. The multiplication is done: The multi-
plicand (123) stays in the input unit, the multiplicator (45) is in the
counter and the result (5535) is in the arithmetic unit.

Example:     22 : 7  =  3.14285714  Remainder 2

Division requires 3 steps:

(A) To Set the Dividend into Arithmetic Unit:
    Enter the dividend (22) into input unit. Press the JUMP [<16] key.
    Make a positive (clockwise) turn with the crank to transfer the
    input into arithmetic unit.

(B) To Set the Divisor into Input Unit:
    Clear input and counter unit. Enter the divisor (07) into input unit.
    Press the JUMP [<16] key.

(C) To Divide:
    Make negative (counter-clockwise) turns with the crank (now the red
    indicator is on) until the arithmetic unit shows an "underflow".
    Make one positive (clockwise) turn with the crank. Move the input
    unit with the STEP [->] key one position to the right.

    Make negative turns again ... and repeat this procedure until the
    required number of decimals are calculated...

    The result (3.14285714) is in the counter unit, and the remainder (2)
    is in the arithmetic unit. The divisor (7) stays in the input unit,
    therefore an additional decimal can be estimated...
    ( 2, cause 2 x 7 = 14).

               Have a look at "Calculating Trickies" ...

R E M A R K    adapted from
The FACIT_CM2-16 ( 1959-72 ) has "Double-Back-Transfer":  Either from the
Arithmetic- or  from the Counter-Unit (= Quotient-Register ) the Contents
could be  "back-transfered"  into Input-Unit to continue the calculation.
Therefore FACIT's special "Split-Pin-Wheel"-Principle was dropped because
construction restrictions.  Remarkable also is the soft keystroke of the
10-Block-Unit:  The mechanism use part of the "Tabulator-Spring-Force" to
do the job!
© C.HAMANN           08/30/07