Litton Royal Mini Five

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Calculators: Handheld: Litton Royal Mini Five


		Size (approx):	87mm x 157mm x 37mm (max) (w,h,d) Weight 194g excluding batteries
		Power:	6.0V from 4 x AA sized batteries. It accepts an adapter/charger (undefined) through a socket on the top side to the far left. The on/off switch is located on the left hand side.
		Case:	Constructed from dark grey and beige matt plastic which is quite wedge shaped. A slightly raised and curved neutral display filter gives a bright image. Below this is a black printed metallic sticker with the brand and model name which sits in its own recess. They keys are long travel with a soft but hollow sounding click.
		Display:	8 digit blue VFD, with no ninth digit
		Features:	4 function calculator with selectable constant
		Age:	1974
		Manufacturer:	Assembled in Malaysia for Imperial Typewriter Company Limited, Leicester, England. Serial number 4210162.
		Comments:	Solid desk-top calculator that just about fits in the hand as well. There is no clear on power up so when you switch on all digits light up with random numbers. Archaic logic with no overflow, seven digit negative numbers is a bit of a let down.

Components:	1 x cpu: C-556 (square spiral design) 7417 (week 17 of 1974), 24 pin DIL, 0.6" width black plastic 1 x 8 digit VFD single tube round face display unit; Futaba 8-CT-01A 4B (February 1974), made in Japan 1 x transistor 2 x diodes 4 x capacitors 2 x SIL resistor arrays 3 x resistors 1 x mini-board sealed in cubic-package: Fuji MCT6201 1 x transformer
Boards:	One board acts as the main component board and keyboard assembly on the other side.
Construction:	Remove the screw from within the battery compartment. Then gently prize the top edge away and pop the side lugs by pushing in the front section. Be careful as damage may easily result. Gently remove the front by hinging from the bottom edge.

Logic comments:	The (C/CE) button is used to clear the last number entered and a second press will clear the calculator
	Overflow on number input is suppressed inputting a ninth digit is ignored
	There is selectable constant on all four functions by pressing (K): i.e. (3)(X)(K)(2)(=) gives “6” (=) gives "18", (5)(=) gives “15” and so on. If you key in the (K) before the function then you get a display full of nonsense numbers - a great random number generator?
	Negative numbers are shown with a “-“ in the far left (eighth) digit thereby limiting you to seven digit negative numbers
	An overflow of greater than eights digits (or seven negative digits) shows the answer without a decimal point; you divide by a multiple of ten to get to a workable number. You can apparently just carry on until eventually you reach around 70 digits when the answer reverts to zero - and then you can carry on again!
	Divide by zero shows just the first decimal point, which is not recoverable
	No other bugs found

	The main board houses all the components at the top whilst the keyboard assembly is underneath. The small brown and blue square box to the upper right is a power supply board with five or six components, including a transistor.