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Calculators: Handheld: Rockwell 18R

Size (approx): 75mm (max) x 155mm x 23mm (max)  (w,h,d)
Weight 130g excluding batteries


9.0V DC, 1xPP3 size battery.  Also accepts adaptor (undefined) through top end socket on the left. There is an on/off sliding switch on the left hand side about half way up.
Case: Sturdy stippled brown plastic case with light beige keyboard surround.  The latter is printed with brown text and lines. Red inset display cover.  Lovely lozenge-shaped keys in chocolate brown have a positive click and work well.  The raised Rockwell logo and two vertical edges are painted silver.  
Display: 8 digit LED with bubble lens with no ninth digit
Features: Four function plus percentages and two function memory.
Age: 1975/6
Manufacturer: Rockwell International, Microelectronic Product Division, Anaheim CA 92803.  Assembled in Mexico, US and Foreign parts.  Serial No. 384280.  I have also had a model made in Hong Kong, with no serial number, but the box has 1976 on it and the receipt is dated 17 August 1977 for 4.75..


A classic looking calculator made a little frustrating by the seven digit limit to negative numbers and the pseudo fixed decimal bug.  Original case is padded brown with flip top and tuck in flap.  Minimum components, late date for chip week code and apparent rev 03 reference number means this is a late model.   This calculator was also built as the House of Fraser model 18F in a dark blue case with white buttons.

Components: 1 x cu: Rockwell B5000CC 7603 (week 03 of 1976), 42 pin staggered DIL, 0.6" width ceramic with metal cap
1 x 8 digit plus one symbol bubble lens LED module
2 x capacitors
That's it!
Boards: Keyboard assembly is attached to the main board by the back screws.  Nine pins self located into sockets on the main board.  Main CPU board ref 20167D67-03
Construction: Remove the four screws on the back.  Gently pull out the front keyboard which hinges up from the display surround.  Pop off the display surround by pulling it upwards. Main assembly can be removed by slightly twisting away from the on/off switch.

Logic comments: (CEC) cancels an incorrect numerical entry, pressing a second time clears the calculator
An error results in the display lighting up all decimal points which is recoverable using of (CE/C)
Divide by zero results in "" which is recoverable using of (CE/C)
Negative numbers art shown with a minus sign to immediate left of a number, but as there is non ninth digit you are limited to seven digit negative numbers.
Input overflow is suppressed, keying in a ninth digit is ignored
There is no indication of memory store - you have to remember it
To cancel the memory, store zero
It has automatic constant on all functions
It suffers the pseudo fixed decimal bug: key in (1)(+)(2)(.)(0)(0)(=) to get "3.00" which remains a two digit fixed decimal format until more are required or you use multiply of divide


The box measures approx. 85mm x 183mm and is 32mm deep.  Printed in fill four colour the box comes with its own cardboard inner former to keep the whole thing rigid.

This particular box is not from the example shown above and has a copyright of 1976, made in Hong Kong.  It also has a reference on the bottom panel "Stock No. 18R S01".

18R Manual This (rather bright) manual measures 135mm x 68mm and is printed in two colours, black and orange.  They did not, however, use the orange colour throughout the booklet.  It has 16 printed pages and is fan-fold format.  Quite a good manual even though it is small.

Copyright 1975, Rockwell International.  Ref 2520-D-91 R2 7-75, 226 R11-005