Litton Royal

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Calculators: Handheld: Litton Royal


		Size (approx):	90mm x 150mm x 35mm (max) (w,h,d) Weight 334g including internal rechargeable batteries
		Power:	Internal sealed batteries (6 x AA sized units). It accepts an adapter/charger (Litton AC Adaptor 9.0V DC 200mA, 7.2V DC 120mA) through a socket on the top side to the far left. The socket is a three pin miniature plug. The adaptor has its own red light to tell you when it's charging. The power switch is located on the left hand side in line with the display and is a three positions switch: DC/Off/AC.
		Case:	Solid case made from sturdy two-piece plastic case with a leather-effect pattern. A curved section raises the top area which holds the recessed but flat green display filter. Originally the display escutcheon was painted silver, but my example has worn badly. Below the display sits a black printed metallic sticker with the brand name in its own recess. The keys are hollow sounding and quite long travel.
		Display:	8 digit green VFD, with no ninth digit.
		Features:	4 function calculator with selectable constant.
		Age:	1973
		Manufacturer:	Made in Japan for the Imperial Typewriter Company Limited, Leicester, England. Serial number 82 42724.
		Comments:	Large and sturdy early calculator with basic functions and some serious logic bugs. Whilst the lack of trailing zero suppression is archaic, the divide by zero bug annoying, the handling of up to 88 digits of overflow is just plain confusing. There is no model number on my example - though I think there is a rear sticker missing off mine. It looks like an earlier revision of the Digital 5-T which was no doubt revised to reduce the enormous component count. Amazingly the rechargeable batteries still worked on my example.

Components:	1 x cpu: 251F (square spiral design) 7309 (week 09 of 1973) 24 pin DIL, 0.6" width 2 x ICs: Matsushita M58212 9136, 16 pin DIL, 0.3" width 1 x 8 digit VFD single tube round face display unit; Futaba 8-CT-01 2K (October 1972), made in Japan 18 x transistors 4 x diodes 0 x capacitors 2 x SIL resistor networks 37 x resistors On mini cpu board: 4 x transistors 10 x diodes 8 x capacitors 7 x resistors 1 x transformer 1 x battery pack type 6-S101, The Furukawa Battery Co. Ltd., Yokohama Japan, Voltage 7.2V 450mAh (5 HR)
Boards:	The keyboard unit sits on top of the main cpu board (ref: 8Z605492) which is located on the back a 7-wayconnector to the PSU board.
Construction:	Surprisingly for its age, it is not secured by screws but just the inner lugs. It is therefore very difficult to open without doing some sort of damage so I suggest you do not. Front comes completely off to reveal the whole assembly sitting in the base.

Logic comments:	The (C) button is used to clear the calculator, there being no cancel entry function
	Overflow on number input is suppressed inputting a ninth digit is ignored
	The display is left leading and there is no trailing zero suppression so all digits are always on.
	Negative numbers are shown with a “-“ in the far left (eighth) digit.
	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. Even then the calculator is quite happy with numbers up to 88 digits when the display reverts to "0.0000000" and is then not recoverable.
	Divide by zero shows the counting clock bug; the display shows "0.0.0.0.0.X.0.8." where X (the third digit) is a cycling counting number. If you wait a while you will also see the sixth digit increment so that is part of the count too, but the intervening two digits stay zero.
	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?

	The first scan on the left shows the calculator with the front removed. Notice the very high component count and white ceramic packaged main IC - both signs of an early 70s machine.		You can then lift out the main board which is connected by the white block connector on the left hand side. This reveals the power supply board and Ni-Cad battery pack. To reduce space most of the components are mounted vertically, and then the tall ones bend over.