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Calculators: Handheld: Adler 80C (aka EC21B)

Size (approx):

73mm x 120mm x 19mm  (w,h,d)
Weight 132g excluding batteries

Power: 6V DC, 4 x AAA size battery.  Also accepts adapter/charger (undefined).  Socket is on bottom side on the right.  Socket is 2mm jack-plug, centre negative.   Charging time is quoted as 14 hours.
Case: Square case with back and sides made of one piece of brushed aluminium.  Dark brown plastic calculator body slides down nearly half way to reveal battery compartment.  Pronounced ridges on the side to aid grip.  Squishy but positive action keys in a variety of colours.  Logo and model number is printed on inset aluminium panel.  Logo is also painted on the top side in white.  The green, slightly sloping display filter gives a clean bright image.
Display: 8 digit green VFD (ninth digit for error and negative flags)
Features: 4 function calculator with percentages
Age: 1975
Manufacturer: Manufacturer: TA Vertriebs GmbH, D8500 Nurnberg, Germany.  Type EC 21B, Serial No. 66.757.711
Comments: Unusual slide out design clear display and weighty quality-feeling calculator.  Button colours are a bit of a jumble. Otherwise sound logic let down by negative square roots and no input overflow suppression and stupid ?commercial? inputting system.  Black plastic case is open topped, rigid front and back and very square in design.  It has lower sides to aid calculator removal. Identical inside to the Imperial 90K

Components: 1 x cpu: NEC ?PD943C H55196
1 x 9 digit VFD flat face single tube display
2 x transistor
7 x diodes
7 x capacitors
0 x resistor arrays
9 x resistors
1 x transformer: TDK DCT-05 Japan
Boards: The keyboard assembly (Ref Gico GK135-9 Japan) sits on top of the main cpu (Ref 80SC) board which is held loosely in the case. A 13-way ribbon cable joins th1e two.
Construction: Push the sides down as if to change the batteries.  Whilst gently pulling out the metal sides, continue to pull the body of the calculator down through the metal stops.  Remove the two side screws and lever the back off through the upper coin slot.

Logic comments: The (Cl) button is used to clear last entry of a number and (C) to clear the whole calculator
Overflow on number input is not suppressed, typing in a nine digit number results in a "C" in the far left (ninth) digit, but it is recoverable using (Cl)
An overflow error displays the result and "C" in the far left (ninth) digit ("E" if negative) and is recoverable using (Cl).
Divide by zero results in a  "C" which is not recoverable.
There is automatic constant on all four functions 
Negative numbers are flagged by a "-" sign in the ninth digit thereby allowing full eight digit negative numbers.
The manual calls the input mode ?Commercial calculating principle?, their name for RPN; the desired operator is selected after inputting the number.  To work out 3-9 key in (3)(+)(9)(-).

manual

The manual measures 120mm x 88 mm and has 36 black printed pages.  The text is quite extensive with plenty of examples (you need them) and is in English, German, French and Spanish.  Printed in Japan, reference No. K 930202594 ? 4/75