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Calculators: Handheld: House of Fraser 24HF 

Size (approx):


75mm x 155mm x 25mm (max)  (w,h,d)
Weight 140g excluding batteries.
Power: 4.5V DC, 3 x AA size batteries the far left battery slot is a dummy.  Also accepts adapter/charger (undefined) through a top side socket on the left.  
Case: Brick-shaped calculator with brown matt plastic base and black textured coloured top dominated by smooth cream plastic keyboard surround.  It has the model number and on/off label printed in black.  Raised Logo on the front is painted silver (slightly worn on this example) as are the two side rails.  Small neutral display filter shows the digits clearly. Squashy keys are very positive to use and brown orange colour scheme quite pleasant.  There is a large metallic printed sticker on the back with basic instructions. 
Display: 8 digit blue VFD display with an extra ninth digit on the far left minus and memory indicators.
Features: Four function with square roots, change sign, percentages and four-function memory.
Age: 1976
Manufacturer: Rockwell International, Microelectronic Product Division, Anaheim, CA 92803 made for the House of Fraser. Made in Japan.  Serial No. 106757.066
Comments: Lovely typical Rockwell calculator with sound logic only let down by the negative square roots.  Both the silver trim and any lettering on the keyboard surround have a tendency to rub off so finding good examples is not easy.  Built to last - and they have.  Rockwell made a number of calculators for the House of Fraser; some a direct clone of a Rockwell model, others with different cases.  This is obviously a Rockwell 24RDII.

Components: 1 x cpu: A5901CA 4 7620 (week 20 of 1976) 42 pin DIL 
1 x single glass tube, flat faced 9 digit VFD display
2 x transistors
4 x diodes
7 x resistors
6 x capacitors
1 x smoothing choke; DCT-04B Zebra
Boards: Keyboard board is attached to front by 12 screws and hinges to the main board on 14 stiff copper wires.  Main CPU board (R-14a-5901S) is clip-fixed to the base.
Construction: Remove the two small screws in the battery compartment.  Gently push out the front keyboard which hinges up from the display surround.  Pop off the display surround by using gently pushing a blunt object through the three slots on the rear.

Logic comments: The Clear key (CE/C) is used once to clear an input number and a second time to completely reset the calculator
Overflow on the input of a number is suppressed
The constant function is automatic on all four main operators
Memory storage is flagged by the ninth (far left) digit decimal point alight
Negative numbers are flagged by a "-" sign in the far left (ninth) digit thereby allowing full eight digit negative numbers.
Negative square roots are allowed. 
A divide by zero shows "" and is recoverable using (CE/C)
Overflow shows the result with all decimal points alight and is recoverable by using (CE)