Rockwell 24RD

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Calculators: Handheld: Rockwell 24RD

	Size (approx):	75mm x 155mm x 23mm (w,h,d) Weight 156g excluding batteries
	Power:	6V DC, 4 x AA size batteries. Does accept an adapter (undefined but 4mm plug) through socket on the top at the far left.
	Case:	Sturdy stippled brown plastic case with light beige keyboard surround. Neutral display cover shows a clear view of the numbers. Squashy but positive keys work well. The raised Rockwell logo and two vertical edges are painted silver and have not worn well in this example. The model number is printed on the keyboard surround.
	Display:	8 digit blue VFD display with no ninth digit but two extra red LEDs above the display to indicate memory storage and minus sign.
	Features:	Standard four functions, square root, change sign, percentages and four function memory.
	Age:	1975
	Manufacturer:	Rockwell international, Microelectronic Product Division, Anaheim, California 92803. Made in Japan. Serial No. 104155.25.
	Comments:	Classic Rockwell shape made that bit more desirable by the two isolated red LEDs. Original case is very high quality brown leather-effect with flip over top and tuck in band. Built to last - and it has only the square roots let the logic down.

Components:	1 x cpu: Rockwell A5901CA 7551 (date code week 51 of 1975) 42 pin staggered DIL 1 x 8 digit VFD flat panel faced display; ISE DP89A 5927 made in Japan 2 x transistors 7 x diodes 9 x capacitors 2 x resistor arrays 9 x resistors 1 x transformer; DCT24
Boards:	The keyboard assembly is attached to the front of the calculator via 12 screws and to the cpu board via 12 strong copper wires.
Construction:	Remove the two small screws in the battery compartment. Gently pull apart the sides and pull the front out (hinged at the middle. Pop off the display cover in a similar way.

Logic comments:	(CE/C) is used once to cancel the last number entered and a second time to clear the whole calculator.
	Input overflow is suppressed, inputting a ninth digit is ignored
	Negative numbers are shown with a isolated LED above the display thereby allowing the display of eight digit negative numbers
	There is automatic constant on all four functions
	Divide by zero shows a "0.0.0.0.0.0.0.0." and is recoverable using (CE/C)
	Overflow displays the result of the calculation with all decimal points alight and is recoverable using (CE/C)
	Memory storage is indicated by a second isolated red LED above the display
	Negative square roots are allowed