| Calculators: Handheld: Commodore SR4912
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Size
(approx):
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80mm
x 147mm x 20-40mm (w,h,d)
Weight 124g excluding batteries
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Power:
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9V
DC, 1 x PP3 size battery. It accepts an adapter/charger (centre
positive) located on the top side in the middle. Use adapter DC-505, 707, 708 or
709. There is a power save function that switches the display off. |
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Case: |
Two-piece
stippled black plastic case with silver printed trim. Raised brand name is
also printed silver and has survived well on this example.
Keys in light and dark grey, white and black and a black keyboard
surround. The keys are
short
travel squishy type but work very well. Heavily inset and
tilted red display filter works quite well giving a large
bright display. |
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Display: |
8+2
digit red LED with bubble lens with a ninth digit for negative, error
indications and an intervening digit for negative exponents. The
latter are the same size as the mantissa digits. |
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Features: |
Four
functions plus percentages, change sign, brackets, reciprocal, pi,
register exchange, square root, squares, nth root, logs, trigs, stats,
polar coordinates, degree, radian , gradians and five function 9 store memory. |
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Age: |
1978 |
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Manufacturer: |
Commodore.
Made in Hong Kong serial No. 90899 with another number 201450-04 |
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Comments: |
Workman
like scientific calculator built to last. With 49 keys is this a button monster or what?
The SR prefix of this period indicates Slide Rule (or their name for
scientific).
The "49" may refer to the number of keys, the 12 for the number
of digits (pushing it!) and they have dropped
the "D" for disposable battery version. Considering its
sophisticated functions it is odd that there are no constants, a memory
store bug and no error recovery. |
| Components: |
1 x cpu: MOS (logo) MPS 7561 005
3478 (week code 34 of 1978) 28 pin DIL, 0.6" width.
1 x LED with bubble lens display module
no other components |
| Boards: |
One board doubles
as the keyboard and main cpu board (PCB No. 201478 Rev A) and is fixed to the
front by six screws. |
| Construction: |
Remove the two long screws from
the rear and the back section lifts off easily, hinging from the bottom. |
| Logic comments: |
(C/CE)
is used to cancel the last number entered and a second time to clear
the whole calculator. |
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There
is no constant |
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Input
overflow is suppressed, inputting a ninth digit is ignored |
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Negative
numbers are shown with a "-" in the far left (ninth) digit thereby
allowing full eight-digit negative numbers |
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Divide
by zero shows "E" in the eight digit and is not recoverable |
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Overflow
shows no number with "E" in the left (eighth) digit and is not
recoverable
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Negative
square roots show no result and "E" in
the left (eighth) digit and is not
recoverable
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The
change sign can be used in mid-number entry |
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Memory
store is not indicated; you have to remember it. To store in memory
four use (STO)(4) and (RCL(4) to recall it. |
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It is possible to
store an error state and confuse the memory; try entering 9 x 10 99
(STO)(1) then (M+)(1). You get an error state but after using (C/CE)
the number in memory-1 is corrupt. |
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There is a power save
function; after about 60 seconds the display goes to a single (first
digit) decimal point (except in th error condition where nothing is
displayed). Operation can continue by just pressing the next key you
want - unlike the manual instructions (see below). |
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The (F) or function
key is used to select the operation in the upper label |
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The (XCH) key is used
to exchange the chosen memory register whilst the (X<>Y) key is used
to exchange the calculator's registers |
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There is a power save
function - after about 30 seconds just once decimal point will stay
alight, pressing any key will continue. |
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The fare left (ninth)
digit decimal point reminds you of gradian mode and the far right (first
exponent) similarly for radians. |
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The box to the left measures approx. 87mm x 155mm and is 47mm deep, so not
much else than the calculator went in. It is printed in red, blue,
black and silver so no expense spared. The sides have French and German
text and it is printed in Hong Kong.
Calling this a twelve digit calculator is
rather pushing it. Eight digit mantissa and 2 digit exponent yes, but
the other two digits are used for the minus signs - cheeky!
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