Interton Electronic PC 2008

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Calculators: Handheld: Interton Electronic PC 2008

		Size (actual):	76.0mm x 132.8mm x 26.6mm (max) (w,h,d) Weight 148g excluding batteries
		Power:	6.0V DC, 4 x AA size batteries. It accepts an adaptor/charger (undefined) through a socket on the top side, on the right.
		Case:	A slab-shaped calculator made of beige and grey smooth plastic. A heavily inset, convex red plastic filter gives a little extra magnification of the LEDs for a bright and wide angle display. The lower front area hold a grey printed metallic sticker with the model details. Rather unusually, the on/off switch is also in this lower front area with black printed text for on/off symbols. The large but shallow keys have a short travel and prominent click, so work quite well. However, the white text on the keys is prone to wear.
		Display:	8 digit red LED (flat type) with no ninth digit
		Features:	Standard four functions with constant
		Age:	1973
		Manufacturer:	Made in Germany by Interton Electronic GmbH, 5 Koln, serial No. 123889
		Comments:	Early hand-held calculator that uses a very basic CPU which is riddled with bugs. Interesting to note that the main IC used an IC socket - they must have suspected a high failure rate to go to that expense. The original cover is a box-like with flip over front cover and side popper closing.

Components:	1 x cpu: General Instruments C550 7309 (week 9 of 1973), 24 pin 0.6" width DIL white ceramic package with metal plate cap (mounted in an IC socket) 4 x IC: ITT461 7302 (week 2 of 1973), 14 pin DIL 0.3" width black plastic (display driver) 1 x 8 digit flat LED display unit: Bowmar Optostic 5 x transistors 1 x diode 4 x capacitor 9 x resistor 1 x DC converter transformer
Boards:	The main board sits face down on top of the keyboard assembly and is held away by two metal spacers with screws through the board. They are joined by 19 stout wires. The keyboard assembly is fixed to the front using the spacing pillars and two extra screws.
Construction:	Remove the five screws from the rear and the rear section will easily lift off to the right.

Logic comments:	The (CE) key operates as a cancel entry function and the (C) will clear the calculator
	In the above example the calculator powers up with data so (C) needs to be pressed first - I do not know if this is a failed auto-clear on power up circuit - more information is required - can anyone help?
	The default display is "00000000" and leading zeros are not suppressed during input, trailing zeros after the decimal point are not suppressed on display of result
	Input overflow is suppressed, inputting a ninth digit is ignored
	Negative numbers are shown with a "-" in the far left (eighth) digit thereby only allowing seven digit negative numbers
	There is selectable constant on all multiply and divide only by using (K)
	Results that overflow have no effect - you just carry on calculating
	Divide by zero shows "0.0.0.0.0.n.0.8." where n is an incrementing number (and after a while the third digit started incrementing looking like is is flagging thousands) and is not recoverable
	It suffers the lagging decimal point bug: key in (.)(3)(3)(3)... etc to eventually get a display of "3.3333333" which is still actually 0.3333333 in calculations
	It suffers the divide to negative zero bug: key in (0)(-)(1)(=) to give "-1" now divide repeatedly by ten to eventually get "-.0000000"

The manual measures 73mm x 133mm and consists of 24 pages in total, printed in black only. It states to cover both this model and the PC2010. In German only.

However, the model pictured inside is clearly a semi-RPN model from the (+=) and (-=) keys so this is either not the correct manual, or they revised the calculator and did not revise the manual. There were two version of both the 2008 and 2010 models.

Also strange that they used the twisted word "Electonenrechner" but stated Germany rather than Deutschland.

This scan shows the only keyboard layout in the manual. I believe this is the PC2010, but pictures on the web show a slightly different model, closer to the one above. Very different model. I'm also intrigued about the 0/00 key as no example of its use is given in the manual.

Based on this manual the two models are eight and ten digit versions.

Can anyone help with either issue?

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