Litton Royal Digital 5-T

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Calculators: Handheld: Litton Royal Digital 5-T

		Size (approx):	88mm x 150mm x 35mm (max) (w,h,d) Weight 184g excluding batteries
		Power:	6.0V DC, 4 x AA size batteries. Accepts an adapter/charger (undefined) through a socket on the top side, on the far left. Battery life (standard) is quoted as 4-5 hours whilst recharging batteries takes 12-16 hours.
		Case:	More designed as a small desktop I would have thought. Two-piece mottled black plastic case with very unusual bowed up display area that is not titled. Printed panel with logo and model sits in its own recess. Bold black and white keys are long travel with a soft snap at the end and work very well. Green display filter gives a very bright and clear image. The three position on/off/charge switch is on the side to the left of the display.
		Display:	8 digit green VFD with no ninth digit
		Features:	Standard four functions with selectable constant key
		Age:	1973
		Manufacturer:	Assembled in Malaysia for Imperial Typewriter Company Limited, Leicester, England. Serial No. C11585.
		Comments:	Lovely relic! The display on this calculator starts up with "00000000" and continues to have no leading zero suppression. Original case is soft black plastic (lined) with left-top-right full zip and top carrying strap. It has the Litton name and logo in silver on the front.

Components:	1 x cpu: C-570 (square spiral design) 7335 (week 35 of 1973) 24 pin DIL. 1 x 8 digit VFD single tube round face display unit; Futaba 8-CT-01A 3K, made in Japan 2 x transistors 5 x diodes 6 x capacitors 2 x SIL resistor networks 8 x resistors 1 x converter unit (Fuji MCT 28103K21) with extra components on a mini board 1 x transformer
Boards:	The keyboard unit sits on top of the main cpu board (ref: 31213486) which is located on the back via four plastic posts.
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 (CE) key is used to cancel an entry whilst the (C) key clears the whole calculator
	Input overflow is not suppressed, inputting an ninth digit results in an error which is recoverable using (CE)
	Negative numbers are shown with a "-" in the immediate left digit travelling into the ninth digit thereby allowing full eight digit negative numbers
	There is selectable constant on all four functions; to multiply a series of numbers by n use (a)(X)(K)(n)(=), (b)(=), (c)(=) etc.
	Divide by zero shows "E" in the far left (ninth) digit and "0." as the result and is not recoverable
	Overflow shows "C" (or "E" if negative) in the far left (ninth) digit and is not recoverable
	All digits are always alight as there is no leading (in front of the number) zero suppression.

The manual measures 152mm x 89mm and is printed in two colour (green and black) throughout. It is in six printed page overlap-fold, so is quite basic considering how expensive this calculator was in its time.

Litton Imperial typewriters & Business Equipment, Glenfield Trading Estate, Old Mill Lane, Kirby Road, Glenfield. Leics. No other references.

Inside

This shot was taken with the front of the case removed. The display is "switch on" and in its "clear state" with all digits showing zero. You can clearly see that the VFD tube has connectors both ends and the metal plate cap on the IC - both signs of early components. The little brown box with blue label on the left is crammed with components - part of the voltage transformer circuit.

This high component count is also a sign of an early (1973) pocket calculator. By the late 1970s there would be only the IC and display.