Decimo 2001-e

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Calculators: Handheld: Decimo 2001-e


	Size (approx):	73mm x 148mm x 18mm (max) (w,h,d) Weight 124g excluding batteries
	Power:	3V DC using 2 x AA size batteries. It accepts an adapter (DC 3V undefined) through a socket on the top side to the far right. The battery compartment is a bit of a squeeze, being quite small.
	Case:	Made of a two-piece matt black plastic case in a slim brick-shape design. The front has a large brushed aluminium panel surrounding the display which is printed with black text for the brand, model number and remarkable description; "electronic slide rule extraordinary" ! The red display filter is flat and flush and gives a nice bright, wide angle image. Just below the screen are on/off and angle switches labelled in raised text. The small keys are short travel load click type and work well on my example. Both vertical sides are covered in matching aluminium panels.
	Display:	10+2 digit flat red LED display with additional two digits for negative and error indicators.
	Features:	Standard four functions with change sign, register exchange, pi, powers, square root, reciprocal, logs, trigs and four function memory. 10+2 scientific display mode (default) with switchable degrees, radians, gradians.
	Age:	1975
	Manufacturer:	Made in Hong Kong, serial number inside battery compartment 510230
	Comments:	Most unlike Decimo's usual designs. In fact the keys remind me more of a Commodore. It has a lovely flat red LED display that is easy to view but all digits light all the time as there is no trailing zero suppression. Logic is very sound but lack of recovery annoying. A lovely early scientific calculator to hold and use. The original case is soft black plastic with top flap that tucks into the front. This flap has an internal stiffener.

Components:	1 x cpu; Rockwell A4800PC 7522 (week 22 of 1975), 42 pin staggered DIL, 0.6" width 2 x display driver ICs: Texas SN75494N P7519 (week 19 of 1975), 16 pin DIL, 0.3" width 1 x 14 digit flat red LED display unit; National Semiconductor with shallow bubble lens 8 x transistor 19 x diodes 6 x capacitors 10 x resistors 1 x transformer
Boards:	The main cpu board (IGI 3008) sits clipped onto the front of the calculator and is joined to the main keyboard assembly via a 21-way connector
Construction:	Very difficult to open as this case is held together with internal lugs only - I do not recommend trying to open it for fear of damage. The easiest way I found was to use a finger nail to prize out and push in the rear section on one of the sides. Even though there appears to be a coin- slot on the back - this is useless. Eventually the rear section will lift off.

Logic comments:	(C) clears the last number entered on its first press and clears the whole calculator on the second
	The display defaults to 10 digit mantissa and 2 digit exponent; there is no trailing zero suppression so all digits are always alight. The only exception to this is the display of zero. The mantissa is left reading rather than the more common right reading used these days.
	Input overflow is suppressed, inputting an eleventh digit is ignored, however, inputting a tenth digits causes the exponent to be displayed automatically
	Negative numbers are indicated by a minus sign in the far left (fourteenth) digit thereby allowing ten digit negative numbers
	There is automatic constant on all four functions
	The change sign function can be used in mid entry
	Divide by zero shows zero and an upper "o" in the far left (fourteenth) digit and is not recoverable
	Overflow shows zero and an upper "o" in the far left (fourteenth) digit and is not recoverable
	Negative square roots are not allowed, show an overflow and is not recoverable
	There is no indication of memory store - you have to remember it!
	(X<>Y) allows you to exchange the last number entered whilst (X<>M) exchanges the current display for the memory contents

	This scan of the calculator with the rear of the case removed exposes most of the innards quite well. The unique Rockwell staggered pin central IC can be easily seen as well as the two display driver ICs at the top. The connector to the (underneath) keyboard assembly can be seen as the blue plastic strip at the bottom. The high component count (especially ICs, transistors and diodes which would be fabricated on board the main IC in later chips) shows that this is a relatively early LED pocket calculator.