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Calculators: Handheld: Casio CQ-1 (Computer Quartz CQ-1)

Size (approx): 143mm x 65mm x 23-30mm (w,h,d)
Weight 124g excluding batteries

Power:

1.5V 1 x AA size battery and 3V through 2 x button cells.  It accepts an adaptor (AD-1S, 0.15W) through a socket on the top side in the middle.  The button cells have their own secondary battery compartment cover.  Quoted lifetime for batteries is one year (for silver-oxide) and 10 hours for the AA dry battery.
"The CQ-1 is operated by two different types of batteries for the clock and the display.
For clock: Two silver-oxide batteries (G-13) (The batteries supply power for alarm, stopwatch and calculator functions.)
For display: One AA-size dry battery (UM-3) or AC power (The AA-size battery supplies power for display of time, calendar, entry, calculation result etc.)."
Case: Horizontal format two-piece case in dark brown matt plastic.  The front is dominated by a single piece metallic plastic trim that covers all edges. Within this trim is a recessed metallic sticker with black and green printed text for the brand and model number.  There is also a recessed grill for the sounder. The display is raised by about 35 degrees so that it can be easily viewed on a desktop. The neutral display filter has a white printed border and text on the surface and days of the week printed underneath it.  Below this switch labels are printed in white also.  The calculator keys are tiny, long travel and squishy.
.Display: 8 digit blue VFD, with no ninth digit for additional indicators.
Features: 4 function calculator with clock, stopwatch and four alarms.
Age: 1975-1977 (this example is 1977)
Manufacturer: Casio Computer Company Ltd.  Made in Japan, serial No. 1995553 on the inside of the main battery compartment.
Comments:

 

The very first attempt by Casio of mingling a digital clock with calculator, though the latter is very basic indeed.  With no recovery, minimal functions and negative zero bug, one wonders why they bothered.   My example has a rather dim display which is not surprising as it relies on the one battery for everything.

Components: 1 x cpu: NEC uPD578C K71089, 28 pin DIL, 0.6" width
1 x IC: NEC uPD876C E72216, 22 pin DIL, 0.3" width
1 x 8 digit VFD display single glass tube; Toshiba E6549 7D (April 1977)
6 x transistors
11 x diodes
12 x capacitors
1 x resistor trimmer
1 x variable capacitor
1 x quartz crystal
13 x resistors
1 x transformer
1 x sounder
1 x inductor
Boards: The main cpu board (E8P-1A) sits over the keyboard and is held in place by a plastic lug.  The two boards are coupled with 23 strong copper wires.  The keyboard assembly fixes to the front via seven screws. A small piggy-back board holds the voltage transforming components. Am earthed shield covers the inside rear of the calculator case.
Construction: Remove the screw from the back.  This is of little help as the whole case is held together by internal lugs.  It is very easy to damage this calculator so my advice is don't try.  Anyway, the best way is top push in the lug that you can see within the battery compartment whilst gently pushing out the brown plastic.  After about a half-hour it will pop.  There is then one further along and two more on the other bottom edge.

Logic comments: There is a master mode switch for ST (Stopwatch), OFF, TIME (for clock), COMP (for calculator) and SET (for the clock and alarms)
The (C) button is used to clear last entry of a number and the (AC) to clear the whole calculator
Overflow on number input is suppressed, typing in a nine digit number ignores the ninth digit
An overflow error is flagged with the no answer just "E." in the first (right most) digit and is not recoverable
Divide by zero results in "E." being displayed in the first (right most) digit and is not recoverable
There is selectable constant on all four functions by double pressing the function; i.e. (5)(X)(X)(4)(=) gives "20", (=) gives"100"
Negative numbers are shown by a "-" in the immediate left digit but as there is no ninth digit you are limited to seven digit negative numbers
This calculator suffers the negative zero bug; try (1)(-)(2)(=) to give "-1" then (+)(1) will give "-0"
To set the time you also have to input the date; switch mode to SET then YY (DT) MM (DT) DD (DT) H (TM) M(TM) (optional +) (TIME) where the optional plus denotes PM.  It is not Y2K compliant.
To display the time switch the mode to TIME and press the TIME key which will display "day date" "hour" "minute" and a decimal point will indicate the day.
To set the alarm is easier; switch mode to SET and key in (6)(TM)(3)(0)(TM)(Alarm)(1) will put 6.30 am into alarm one, there being four different alarms.  Again, an optional (+) before pressing alarm will make is PM.
To use the stopwatch switch the mode to ST.  The (TIME) key becomes the start/stop and the (LAP) key freezes the display