APF Mark 42

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Calculators: Handheld: APF Mark 42

		Size (actual):	67.0mm (max) x 126.5mm x 27.1mm (max) (w,h,d) Weight 70g excluding batteries.
		Power:	9.0V DC, 1 x PP3 size battery. Also accepts adaptor (7.5V 100 mA, 2.5mm jack-centre positive) through a top side socket on the far left. A piece of foam is stuck inside the battery compartment to stop the battery rattling around.
		Case:	Two piece matt black plastic case which is slightly squeaky and hardly a straight line anywhere. A brushed aluminium display escutcheon sits proud, with a recess for another brushed aluminium brand and model name plate. Soft blue and white key colours are very nice - operating with a soft click. A recessed and tilted red plastic display filter gives a bright clean display but with a limited viewing angle.
		Display:	8 digit red LED with bubble lens display - no ninth digit.
		Features:	Basic four function with percentages.
		Age:	1979
		Manufacturer:	APF Electronic Inc. New York NY 10022. Made in Hong Kong. I have had serial numbers 42-140915 and 42-131027.
		Comments:	Compact and quite nice LED calculator with nice display despite the bubble lens. The logic is let down by seven digit negative numbers and the pseudo fixed decimal bug. Absolute minimum of components and probably one of the last LED calculators.

Components:	1 x IC: Texas Instruments TMS0972NL MBT 7849 (week 49 of 1978), 28 pin DIL 0.3" black plastic 1 x eight digit LED unit: National semiconductor NSA1188 That's it.
Boards:	The main board (oD42 MS0972) sits face down, loose on top of the keyboard assembly. It is connected with 14 strong wires which go through plastic separators. The IC has a sticky foam pad on it to keep then apart. The keyboard assembly is fixed to the front of the case by six screws.
Construction:	Quite difficult to open as it is held together with internal lugs only. I would not recommend it as damage may result. First loosen the adaptor socket's fixing ring and then try to pop the lugs (three on each side), by pushing in the back section. The rear eventually lifts off.

Logic comments:	The Clear Entry key (CE) is used to clear an input number, the clear (C) key is used to completely reset the calculator
	Overflow on the input of a number is suppressed, keying a ninth digit is ignored
	The constant function is automatic on all four operations - nicely indicated by the (=/K) key
	The negative sign is shown on the immediate left digit but as there is no ninth digit then you are limited to seven digit negative numbers
	Overflow errors are shown as a flashing number which is recoverable by use of the (CE) key
	A divide by zero or overflow error is shown as a flashing "0" which is recoverable by use of the (CE) key
	It has the pseudo fixed decimal bug: key in (1)(+)(0)(0)(0)(=) to get "1.000" which stays a three digit fixed decimal until you need more or use multiply or divide

This box is calculator-sized at 148mm x 70mm x 30mm and printed in silver and black.

There is an inner former, which is about the size of a nine volt battery - so I assume it was supplied with one.

Says Made in Hong Kong, but no other details.

18pp fan-fold manual printed in dark cyan. Good diagrams and extensive instructions.

Innovative Marketing International Ltd.
Nine Park Road
Baker Street
London NW1 6XN

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