Decimo Realtone 9202

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Calculators: Handheld: Decimo (Realtone) 9202 (aka Memory)


		Size (approx):	114mm x 193mm x 45mm (max) (w,h,d) Weight 462g excluding batteries
		Power:	6.0V DC, 4 x C size batteries. Also accepts adapter (6V DC 200mA) through a top side socket on the right. Remove plug from jack to operate from batteries. Innovative two key on/off system. Low battery indication.
		Case:	Large heavy battery-desktop machine that was built to last. The case is made from two-piece mottled black plastic top and bottom and has thick metal panels on the sides and bottom. The latter has some black printed text "MEMORY AUTOMATIC ELECTRONIC CALCULATOR". The top front has a large plastic sticker with the Decimo branding. The area also has a recessed metallic sticker, printed in black and blue, with the Realtone brand. It also has some ridges that look like they should be cooling slots - but as they are filled in there are just there for show. The keys are large, long travel and hollow sounding but work well enough. The neutral display filter is quite inset and heavily tilted with white text for the numerals and symbol display. There are raised areas printed with white text for the switch labels. The rear has a large sticker with loads of calculation info, a smaller one for battery orientation info and a strip (that looks like it could be removed) with model and branding info.
		Display:	8 digit blue VFD with a ninth for negative, overflow and memory indication
		Features:	Standard four functions with percentages and two-function memory. RPN logic. Switched for memory and fixed decimal /financial input.
		Age:	1973
		Manufacturer:	Rear label states Realtone Electronics Inc., model 9202. made in Japan, no serial number.
		Comments:	Strange one this as it appears to be exactly the same as the Vatman Boss (aka Memory), which is a branded version of the Kingspoint /Realtone 9202. The only difference being that the lower edge has different printed text (hence a scan is included here) and the Decimo badge is in a different place. There are many other brands that look very similar as well as associated models like the Decimo 9100. Who knows what it really is! However, as a sturdy early desktop calculator it is extremely well built. The logic, whilst archaic with the Reverse Polish Notation, is quite sound and only let down by the pseudo fixed decimal bug. The unusual two-key on/off system does not take advantage of an auto-power down function. There appears to be no reason for the extra two white dots either side of the display unless they are printed for a 12 digit model. Lovely!
		Comments:

Components:	1 x cpu; Rockwell 15330PB 7338 (week 38 of 1973) ,42 pin staggered DIL, 0.6" width black plastic, metal top 1 x 9 digit VFD; single tube round face: NEC LD8076 15 x transistors 14 x diodes 1 x bridge rectifier 7 x capacitors 1 x variable capacitor 23 x resistors 3 x resistor arrays 1 x transformer: PCT-011 TDK Japan
Boards:	The main board (P-601) is screwed to two support pillars and two brackets. and connected to the keyboard assembly (2006) via a full-width edge connector.
Construction:	Remove the two screws from the back and the two inside the battery compartment. The rear will then lift off easily.

Logic comments:	The Clear (C) is used to once to clear an input number, and a second time to completely reset the calculator
	Input overflow is suppressed: inputting a ninth digit is ignored
	There is automatic constant on multiply and divide only
	The Logic is RPN; i.e. to work out 4-5 key in (4)(+)(5)(-) to give "-1"
	The negative sign is shown in the far left (ninth) digit thereby allowing full nine digit negative numbers
	Overflow shows the result and "C" (or "E" if negative) in the far left (ninth) digit and is recoverable using (C)
	Divide by zero shows zero and "C" in the far left (ninth) digit and is recoverable using (C)
	The memory is activated by using the MR switch where the result of any "=" is stored and any multiply or divide calculation is completed
	Memory store is indicated by the far left (ninth) digit decimal point alight
	Reciprocals can be performed by: (C)(n)(/)(/)(=)
	It suffers the pseudo fixed decimal bug: key in (1)(+)(0)(.)(0)(0)(0)(+) to give "1.000" which remains a fixed three digit number until more digits are needed or you use multiply of divide
	A switch allows you to select floating decimal mode (F), two digit fixed decimal (2) or financial ($) input mode.
	Low batteries are indicated by "........" on the display
	The rear label states that after an overflow "No further calculation can be made", which is not true as (C) allows you to clear the error state and carry on, albeit with a shifted number.

	The main board shown here is typical of this early single-chip 1970s type: a large number of transistors (and other components) and built to last. Sturdy fixings and transistor heat-sinks (the metal bits on the lower left) show that no expense was spared. Notice the black paper surrounding the VFD tube to cut out stray light, and the typical staggered pin Rockwell chip. This board looks exactly like the Vatman Boss cpu board that can be found on the web.