Adler 81

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Calculators: Handheld: Adler 81 (aka EC11)

		Size (approx):	70mm x 119mm x 22mm (w,h,d) Weight 142g excluding batteries
		Power:	4.5V DC, 3 x AA size batteries. Also accepts adaptor/charger (type AD2, odd two pin socket). This socket is on top side, in the middle. Alkaline Magnesium batteries are quoted for operation of approx. 10 hours. Do not use the adapter with standard batteries in place. Also, do not set the switch to battery picture whilst on adapter as this will discharge the batteries.
		Case:	Leading edge or what! The main case body is a three-piece black smooth plastic case with rounded box key surrounds. A sliding u-shaped metal back unpainted. The back is pushed up to reveal the battery compartment and inner information label. A brushed aluminium wrap around panel sits in its own recess and is printed black with abstract symbols for adapter/battery power (on/off), floating/round-off and auto-memory. The red display filter sits (almost) flush and gives a clear bright image. The designer round keys are short-travel squishy type but work well.
		Display:	8 digit red LED with a ninth digit for error and negative indication
		Features:	4 function calculator with percentages, switch accumulating memory and switched floating point modes
		Age:	1973
		Manufacturer:	Manufacturer: TA Vertriebs GmbH, D8500 Nurnberg, Germany. Type EC11, Serial No. 948568 embossed on one side.
		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 a pseudo fixed decimal bug and archaic semi-RPN inputting system. The cover is black stiffened plastic with flip over top. Very similar to models from Anita.

Components:	1 x cpu: Rockwell 15330PC 7320 (date code week 20 of 1973), 42 pin staggered DIL, 0.6" width ceramic case 1 x 9 digit LED flat face single display 10 x transistor 2 x diodes 1 x capacitors 0 x resistor arrays 19 x resistors On the keyboard unit: 1 x diode On the power board: 3 x transistors 3 x diodes 2 x capacitors 3 x resistors 1 x transformer
Boards:	The keyboard assembly (1895 PC 811 Keyboard Iss. 3 TB3606) is attached to the first (cpu) board (Ref 1970 PC Iss. 1 MAIN BD TB3754) via 16 strong wires which is attached to the second (power converter) board (Ref. 1852 PC Iss. 7 TB3528 Convertor BD) via 14 strong wires in the same place. The latter board has two circular cut-outs to allow the tantalum bead capacitor and transformer to sit through and minimise the thickness. The two boards are kept apart by sliders in the main case sides.
Construction:	By gently pushing out the metal sides you can fully remove the u-shaped back. Surprisingly the underside of the main board is then exposed. Remove the two side screws and the base drops off (be careful not to lose the two square washers). The upper and side section then pull away to leave the keyboard attached to the main assembly.

Logic comments:	The (C) button is used once to clear last entry of a number and again to clear the whole calculator, so it is a CE/C key really
	Overflow on number input is suppressed, typing in a ninth digit is ignored
	An overflow error displays the result and "C" in the far left (ninth) digit ("E" if negative) and is recoverable using (C).
	Divide by zero results in a "C" which is also recoverable.
	There is automatic constant on multiply and divide only
	Negative numbers are flagged by a "-" sign in the ninth digit thereby allowing full eight digit negative numbers.
	The logic is RPN, to work out 3-2 key in (3)+(2)(-)
	A switch enables the automatic memory Accumulator "A", when all answers are added to the memory when you hit (=), use (CM) to clear memory and (MOUT) to recall memory, there is no indication of memory
	A switch changes between fully floating point mode "F" and fixed two digit, rounded mode "5/4"
	It suffers the pseudo fixed decimal bug: key in (1)+(1)(.)(0)(0)(+) to get "2.00" which stays a fixed two digit decimal number until more are needed or you use multiply or divide

	The manual measures 120mm x 69 mm and has 16 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 England. It has an odd half page that pulls out describing the battery system. Buy this manual on PDF.
	Early LED displays used rows of diodes in lines. They are characterised by the lack of bubble lens over each digit and so take on a rather flatter appearance. The Adler 81 is easier to read at an angle but the digits are small and often not very bright.