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Calculators: Handheld: Sinclair Scientific
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Size (approx): |
50mm
x 100mm x 18mm (w,h,d) |
| Power: | 6V DC, 4 x AAA size batteries. It does not accept an adapter/charger. | |
| Case: | Two-piece smooth white plastic case which is designed just about as small as is practical. A raised escutcheon frames a deep purple display filter that gives quite a good, if narrow view of the digits. The keyboard surround is in contrasting black plastic with white printed key labels. The grey and blue keys are short travel and give a prominent click but work well enough. The company and calculator name are printed in black along with a few "handy" constants. | |
| Display: | 8 digit red LED with bubble lens with a ninth digit for negative indication. | |
| Features: | Four functions plus trig and limited log functions. RPN logic. | |
| Age: | 1974 | |
| Manufacturer: | Sinclair Radionics of Cambridge, UK, made in England, I cannot find a serial number on my example. | |
| Comments: | A classic early pocket calculator famous for its affordability and small size. This is one of the earliest of the small white case (often named Cambridge) types. A must for everyone's collection because it is so weird. Original case is shaped, hard two-piece black plastic with clasp closing at the bottom. The case has a handy cheat sheet stuck on the inside to remind you of calculation orders. Reverse Polish Notation explains the lack of an equals key. Odd single display format is even stranger. Logic is dreadful along with the double function shift keys and limited scientific functions. Strange strange strange! When you open the battery compartment you rest the batteries on an exposed circuit board - disaster if they ever leak. You can see a later advert for this home kit calculator from 1976. |
| Components: | 1 x cpu: Texas TMC0805NC 7424
(week 24 of 1974) 28 pin DIL, 0.6" width 1 x display driver IC: Texas IFC1 7448, 16 pin DIL, 0.3" width 1 x IC: (timer?) no markings, 8 pin DIL, 0.3" width 1 x 9 digit bubble lens LED module: Bowmar 3 x diodes 3 x capacitors 5 x resistors 1 x open transformer |
| Boards: | Single board that sits lose in the case hold the keyboard on one side and the cpu and components on the other |
| Construction: | Lugs hold the two sides together all around - three on the sides and one each top and bottom. High potential for damage trying to open it so beware. |
| Logic comments: | (C) is used to clear the calculator, there being no cancel entry function that I can find. The Clear function is essential in RPN calculators to stop you getting mixed up with the last calculation. |
| There is no automatic constant but RPN gets close; (C)(5)(+)(X) gives 25, (X) gives 625. | |
| RPN means odder than normal calculations; 6-2 is keyed in as (C)(6)(+)(2)(-) to give 4 | |
| The display is in a permanent fixed four decimal point 5 digit mantissa and 2 digit exponent mode | |
| Input overflow is suppressed, inputting a sixth digit is ignored | |
| Negative numbers are shown with a "-" in the far left (ninth) digit thereby allowing full five digit negative numbers | |
| You can select functions by using the up-shift (^) and down-shift (V) keys | |
| Whilst there are no square roots the case guide shows you how to use logs: to find the square root of 2 use (C)(2)(^)(X)(2)(/)(V)(X) or the nth root of 2 use (C)(2)(^)(X)(n)(/)(V)(X). | |
| Divide by zero is completely ignored and you can carry on! | |
| Overflow is impossible it just carries on calculating with shifted results! | |
| You may very well own one of these and think that it doesn't work properly! |
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