Binatone President

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Calculators: Handheld: Binatone President (aka model 02-4309)


		Size (approx):	74mm x 139mm x 20mm (max) (w,h,d) Weight 122g excluding batteries.
		Power:	3.0V DC, 2 x AA size batteries. Also accepts adaptor/charger (3.0V DC, 0.3W) through a prominent top side socket to the far right. The battery compartment has a red ribbon-pull to aid battery removal.
		Case:	Two piece matt black plastic case with substantial brushed aluminium panels either side giving it a quality feel. At the top is a raised recess area that holds a black printed metallic sticker with the brand and model name. Below this is an oversized green plastic display filter that sits recessed and has white printed numeral indicators. The keys are medium travel with a soft click, each with their own raised area, a lot like Commodore keys. Embossed text is uses to label the on/off switch.
		Display:	8 digit green VFD with a ninth digit for negative, memory and error indication.
		Features:	Basic four function with percentages, change sign, square root and two-function memory.
		Age:	1975
		Manufacturer:	Undefined, art. number 02-4309, made in Taiwan, Republic of China. Whilst the back label has an area for a serial number, my example does not have one.
		Comments:	Sturdy, wide but slim calculator that is a bit odd because of the prominent power socket. The back label boasts "8-digit Electronic Calculator with 1 Memory". The logic is pretty poor with no recovery, simple memory and negative zero bugs.

Components:	1 x IC: Sharp LI2003 5B1 002 (week 1 of 1975), 28 pin DIL, 0.6" width white ceramic with gold metal round plate seal 1 x 9 digit VFD module, single glass tube flat face: Futaba 9-ST-12 5C (March 1975) 2 x transistors 5 x diodes 5 x capacitors 4 x resistors 2 x resistor arrays 1 x transformer: TDK SR-10-SF Taiwan
Boards:	The main cpu board (SR-101-A1) sits on the rear section with a foam sticky pad and to the front with four guide plastic lugs. The keyboard assembly attached to the front and covered by a plastic sheet to insulate the connections. The two are joined together by 13 strong wide wires. The main board has printed marks for components not there, so may have been used for more than one model.
Construction:	Remove the screw from the rear. This does not help a lot as the case is held together by internal lugs. There is a "coin slot" at the bottom edge that can be used to lever the case apart - with great care and a blunt, soft instrument. Eventually the two halves can be separated, hinging from the bottom with limited opening unless you loosen the adapter socket.

Logic comments:	(C) cancels the last number entered whilst a second press will clear the whole calculator
	Input overflow is suppressed; inputting a ninth digit is ignored
	There is automatic constant on multiply and divide only
	Negative numbers are represented by a "-" sign in the far left (ninth) digit thereby allowing full eight digit negative numbers
	Overflow shows the result and "C" (or "E" if negative) in the far left (ninth) digit and is not recoverable
	Divide by zero results in zero and "C" in the far left (ninth) digit and is not recoverable
	Memory store is indicated by the decimal point of the far left (ninth) digit
	To add to the memory use (+M), to recall use (MT), to cancel use (MT)(MT)
	The change sign function can be used in mid number entry but not before
	Negative square roots are not allowed and result in zero and "C" in the far left (ninth) digit and is not recoverable
	Overflow in memory stores the original number
	It suffers the pseudo fixed decimal bug: key in (1)(+)(.)(0)(0)(0)(=) to give "1.000" which remains a fixed three digit decimal number until you need more digits or use multiply or divide
	It suffers the negative zero bug: key in (1)(-)(2)(=) to give "-1" then (+)(1)(=) to give "-0". It also suffers the divide to negative zero bug.