Hand-held Calculators

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Sharp EL-8, Facit 1111, & Addo-X 9364

The Sharp EL-8 was one of the first hand-held calculators. Sharp also put the same electronics into different cases to produce calculators for sale by Facit and Addo.

Sharp EL-8 (aka Compet ELSI-8)

Sharp  EL-8 Picture

Sharp EL-8 (aka Compet ELSI-8)

Distinctive features: One of the first hand-held, battery powered calculators.

Technical details:
Display is 8 digits green "Itron" fluorescent tubes.
Note the strange shape of the numerals and the half-height zero clearly shown in the photograph of the Facit version below, distinctive of Japanese-made calculators of this time.

Four-functions.
The keyboard on this calculator has the number of keys reduced to the minimum by the use of only three function keys, including a combined "x" key.
Here, pressing "x" gives the multiplication function if "+=" is subsequently pressed to give the answer, and gives the division function if "-=" is subsequently pressed to give the answer, so:
4 x 2 +=  gives the answer 8.
4 x 2 -=  gives the answer 2.
This keyboard is further explained in the page about Calculator Keyboard Layouts.

Main integrated circuits - Rockwell NRD2256, AC2261, DC2266B, AU2271B, CG1121. The four large-scale integrated circuits (LSI) are for the calculating functions, and the integrated circuit in the small can is the clock generator..

7.2v (6 x AA) re-chargeable battery giving three hours operation.

100 mm x 163 mm x 67 mm (4" x 6.5" x 2.7").

In June 1971 in the U.S.A. the cost was US$345[1] (about 145).

Made in Japan.

The keyboard is notable for its use of only 15 keys. Multiplication and division are combined in one key, but the operation actually used is determined by whether the += key is pressed at the end of the calculation, to give multiplcation, or the –= key, to give division.

There are video advertisements for the Sharp ELSI-8 on the YouTube site at http://www.youtube.com/watch?v=nCcgoTc8AQc and http://www.youtube.com/watch?v=uyaJ3YgtjWo. It is "the world's smallest electronic calculator".

Picture

With the rear cover removed, revealing the very neat and compact way in which the circuit boards and the rechargeable battery pack are arranged.

Inside Sharp  EL-8

After removing the top cover the "Itron" vacuum-fluorescent display tubes can be seen.

Inside Sharp  EL-8
Calculating board

The display board with 9 driver integrated circuits.

The calculating board with 4 Rockwell LSI integrated circuits, and a timer integrated circuit.

This was one of the first hand-held calculators, but is just too big to be called a pocket calculator. The earlier Sharp model QT8-B was the first battery-portable model, but was really a desk calculator adapted with a battery module.
Although it is hand holdable it is not really a pocket calculator due to its great thickness (67 mm / 2.7").

Versions sold by other companies

Facit 1111

Facit 1111

A version made for the Facit Company of Sweden.
Although the case has a different design, the internal electronics are similar.

Note the stylised display used by many Japanese calculators of this time and the half-height zero. The display shows 1234567.0.

Facit were large producers of mechanical calculators, but their electronic calculators appear to have been made by others. In 1972 they were victims of the great drop in the price of electronic calculators and were taken over by Electrolux.

Addo-X 9364

Addo-X 9364

A similar version to the Facit 1111 above. Addo was another Swedish company, and had links to Facit in the 1970s.

The Sharp EL-8 was developed fron the QT-8B portable calculator and uses the same chip set.
The journal "Electronics" reported[2]:
" How to cut a pocket calculator in half
    Limited battery power was the biggest problem faced by Sharp Corp. engineers when they were told to repackage the company's Micro-compet electronic desk calculator into a case with about half the volume of that formerly used. The new case has only enough room for six penlight-size rechargeable nickel cadmium cells, giving a total of 450 milliampere-hours compared with the 1,200 milliampere-hours  available in the earlier model. Even the smaller cells are a tight fit: the, case measures 2.76 inches high by 4.02 inches wide by 6.46 inches long. Weight including cells is only 1.59 pounds.
    Redesign was quite successful - display drain was reduced to 460 milliwatts from 1,480 mW and logic circuit drain was reduced to 100 mW from 375 mW. As a bonus, the redesign eliminated the separate high-voltage power supply for the display.
    The redesigned calculator, called ELSI-8 around the Sharp plant, uses the same four large-scale-integration arrays made by North American Rockwell Electronics. These arrays feature a 4-phase logic scheme in which there is no steady-state dc power drain. Only the small current-1 to 2 mW-needed to charge the small gate capacitances of the driver transistors flows in the logic circuits.
   The lion's share of the power charged to the logic circuit is actually dissipated in the clock generator. The new clock generator reduces drain by three quarters and has better frequency stability. It consists of a static cross-coupled reset-set multivibrator circuit operating at twice the 50-kilohertz clock frequency, followed by logiccircuits for generating the clock signals. An external resistor and an external capacitor set the frequency. The former arrangement was less stable because it used circuit resistance and stray capacitance. The double frequency arrangement cuts the number of logic inverters needed from 250 to 50.
    Display circuit power drain was reduced, and the need for a separate power supply eliminated, by a circuit change that at first glance appears to be a step backward. Instead of using the time division mode pioneered by Sharp several years ago, the new calculator drives each segment of each display tube separately in a static mode. The big virtue of time division is large reduction in driving circuits, but the big disadvantage is that the rapid switching dissipates large amounts of power in load resistors.
     Today, the saving in components is far less important than when the  time division mode was adopted. In the new calculator, segment drive is by MOS FETs with nine driving circuits per package. Nine packages are sufficient to drive all eight digits and decimal points. Load resistors are completely eliminated because the display tubes segments serve as loads on the driving circuits.
    What's more, because the display tubes are operated in a static mode,   the power supply voltage can be reduced from the 55 volts used in the time division mode to 25 V, the same voltage used for the logic circuits. With time division operation, a high supply voltage is needed for high instantaneous brightness to obtain high average brightness because of the short duty cycle."

Rockwell collaborated with Sharp in developing calculator integrated circuits (ICs). A year or two later Rockwell produced its own range of calculators and sold the ICs to many other manufacturers.

 

For further information about Sharp Corporation and its calculators visit the Calculator Companies section of this site.

 

References

  1. "Microelectronics Shrinks the Calculator", Popular Science, June 1971, p74.
  2. "How to cut a pocket calculator in half", Electronics, Feb. 7 1971.
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Hand-held Calculators

TI Cal-Tech
Canon Pocketronic
Sanyo ICC-0081 & ICC-82D
Sharp QT-8B
Busicom LE-120A & LE-120S
Sharp EL-8 & Facit 1111
Minolta Minolcom
Brother PRO-CAL 408
Walther ETR3
Bowmar 901B
Ragen Microelectronic
Compucorp 324G
Sharp EL-811 & derivatives
Royal Digital III & IV
Busicom LE-100A handy
Busicom LE-80A handy
Hewlett Packard HP-35
Canon LE-10
Rapidman 800
Texas Instruments 2500
Lloyd's Accumatic 100
Sinclair Executive
Casio Mini
Sanyo ICC-809
Sharp EL-801
Texas Instruments SR-10
Sperry Remington 661D & 661
Olympia CD 81
apf Mark V
Ramsgate M-11
Olivetti Divisumma 18
Iain Jones International Mini A
Hewlett-Packard HP80
Litronix Checkmate
Heathkit IC-2009
MITS 150
Summit Ko9V, K16 & SE88M
Unicom 102
Victor 85 "Tallymate"
Elka 101
RFT minirex 75
Sharp EL-120
Sharp EL-805
Bowmar MX-55
Atlas-Rand, Berkey, & Keystone
Hewlett-Packard HP-65
Casio fx-10
Calcu-pen
Casio AL-8 & family models
Commodore 776M & 796M
Novus 650 "Mathbox"
Rockwell 8R
General Instrument EZ3000
Check, billfold, wallet calculators
Monte Carlo
Texas Instruments Spirit of '76
Pulsar Calculator Watch
Compuchron Calculator Watch
Adler Lady & Sir
Elektronika B3-18A & C3-15
Speech+
Commodore S61
"Standard Type 1"
Sharp EL-8026
Texas Instruments TI-30
Canon Multi 8
Casio ST1
Wrist Calculators
Kosmos I & Kosmos Astro
Hanimex Calculator-Recorder
Navigation Calculators
TI58 Special Function Calculators
Sandvik 842S Coromant
"Standard Type 2"
Panasonic Electronic Ruler
Teal Photon
Casio Mini Card LC-78
Feet & inches calculators
SCAT Specialist Calculators
Sharp EL-826
Sharp EL-825
Sanyo CX-1
Elektronika MK-33 etc
Sharp PC1211/Tandy TRS80 PC1
Curta
Slide Rule
Otis King L

Vintage Calculators

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