John Wolff's Web Museum

Early Electronic Calculators - Portable

This page shows a selection of interesting portable calculators from a variety of manufacturers, arranged more or less in chronological order. Please refer to the separate brands listings for machines from Canon, Casio, Sanyo, Sharp, and others.

Click on the photos for larger illustrations, or follow the links for further details.


Adler 60 Adler Model EC-60, S/N 65050387
Functions: ASMD
Technology: MOS-LSI (Omron HD 32163P)
Display: 6 digits, vacuum fluorescent tube
Dimensions: 100W x 157D x 43H, weight 360g including batteries.
Manufactured: Made in Japan for TA Vertriebs GmbH, Nürnberg, Germany, 1973

The Adler EC-60 is a very basic four-function portable calculator from 1973. It was supplied with a soft slip case with a carrying strap, but is much too large to be called a "pocket" calculator.

The EC-60 uses a single-chip Hitachi HD-32163P processor (made by Omron) and a single-ended 6-digit fluorescent display tube from ISE. The display digits are only about 4.5mm high. Power consumption is about 120mA (720mW) from four AA batteries or an external AC adapter. The batteries and input socket are held in a removable carrier which clips in to the end of the case, suggesting that an alternative module with rechargeable NiCad batteries may have been available.
EC-60 rear view with battery carrier (23kb).
EC-60 circuit board (32kb).


Monroe 40 Monroe Model 40, S/N F048054
Functions: ASMD, percent
Technology: MOS-LSI, single chip (GI 175A)
Display: 10 digits, 7-segment neon (Panaplex II)
Dimensions: 85W x 150D x 45H, weight 365g.
Manufactured: Monroe Division, Litton Business Systems, USA, 1974

The Monroe Calculating Machine Company first ventured into electronic calculators in the mid-1960s by selling re-badged desktop machines built by Canon in Japan and Compucorp in the USA. This portable Model 40 from 1974 appears to have been designed in the USA by Monroe themselves.

The calculator operates in the traditional adding-machine fashion for addition and subtraction, with separate Total and Sub-total keys. The display shows the last value entered, rather than the running total. Multiplication and division operate algebraically, with a common Equals key and an independent result register. Separate +/= and -/= keys are provided to add the results of multiplications or divisions into the addition register. This arrangement has the peculiar effect that a multiplication or division can be carried out in the middle of a string of additions without upsetting the accumulated total.

The calculator uses a General Instruments 175A processor and a Burroughs Panaplex II gas-discharge display, and draws about 900mW from 4 disposable AA batteries or a rechargeable NiCad pack. The sliding power switch at the front of the machine also serves as the decimal selector, with a choice of 0 to 6 fixed places, adding machine mode (with an assumed decimal point), or full floating point operation.

The distinctive case for the Model 40 was designed by Myron Beitler and Douglas Graham of Monroe/Litton in 1973 (US design patent D236483).
Monroe 40 internals (30kb).


Litronix 1100 LED calculator Litronix LED calculator, Model 1100, S/N 337064
Functions: ASMD, fixed decimal point
Technology: MOS-LSI (single chip)
Display: 8 digits, miniature LED modules
Dimensions: 75W x 150D x 20H, weight 180g.
Manufactured: Assembled in Malaysia by Litronix Inc, Cupertino, CA, 1974

Litronix Inc was established in 1970 to manufacture opto-electronic components based on the new light-emitting diodes (LEDs). The company established a manufacturing plant in Malaysia, and was a major supplier of LED components and displays until it was taken over by Siemens in the 1980s. A range of calculators and LED watches was produced under the Litronix brand to showcase their own displays.

The Model 1100 is a revised version of Litronix's first "Checkmate" calculator, which was part of the 1970s craze for "check-book balancing" applications. Like its predecessor, the Model 1100 is a very basic four-function calculator with a fixed-decimal system. Inputs and results are restricted to either 6.2 or 4.4 format (ie, nnnnnn.dd or nnnn.dddd), according to the setting of the Decimals switch. However, the calculator always operates internally to 12 figures. If the result exceeds the capacity of the selected format, the calculator shows the least significant digits and lights an overflow indicator. The result can then be divided manually by 1000 (or other convenient factor) to retrieve the higher digits. If the result exceeds 12 figures the display shows all zeros, and the caclulator must be cleared in order to continue.

The circuit board carries a 40-pin processor chip identified only by a hand-written paper label. (There are no markings under the label). There are two 16-pin chips adjacent to the keyboard and display, also unidentified. The LED display uses three miniature 3-digit 7-segment modules, with a single overflow LED at the left-hand side. The display modules have built-in magnifying lenses, and have a fairly limited viewing angle. The keyboard is a "click" module from Texas Instruments, with two small slider switches for power and decimal selection. The main circuit board is hand-soldered, and the calculator is assembled with clips, glue, and heat-staked plastic pins.

The calculator draws 40 to 60mA (270mW max) from three AA batteries. A small encapsulated power supply (top, in PCB view) provides the additional voltages needed for the MOS processor.
Litronix 1100 circuit board.


Adler 108T scientific calculator Adler scientific calculator, Model 108T, S/N 68.687.704
Functions: ASMD, scientific functions
Technology: MOS-LSI (single chip)
Display: 8+2 digits, 12-digit vacuum fluorescent module
Dimensions: 85W x 147D x 25H, weight 320g.
Manufactured: Made in Japan for TA Vertriebs GmbH, Nürnberg, Germany, 1975

The Adler 108T is a portable "scientific" calculator from 1975. It provides trig functions and their inverses in degrees or radians, powers and roots, natural and base-10 logarithms, and one memory register with direct memory artithmetic. The calculator uses algebraic entry with two levels of parentheses, but all of the scientific and memory functions require the use of an "F-key" prefix. An "inverse F-key" is provided for the trig functions. Results greater than 8 digits or less than 1 are displayed in scientific notation.

The processor is a single-chip Rockwell LA4802PA dated October 1975, on a circuit board labelled "GICO Japan". The display uses a 12-digit fluorescent panel (Itron FG125A2) to show results in "8+2" format, with the remaining two positions reserved for signs and memory/error indicators. Results from the scientific functions are produced quickly (well under a second), but are only shown to six figures. The circuitry draws 50-60mA (about 300-350mW) from four disposable AA batteries or an external AC adaptor.

The calculator has a black right-angled plastic casing with a wrap-around aluminium sleeve covering the sides and the back. The sleeve slides upwards to reveal the nameplate and to open the battery compartment. The external design is based on an earlier range of calculators developed in 1972 by Rockwell and the Bell Punch Company and sold under the Triumph, Adler, and Anita brands. Further details of the connections between these companies can be found on Nigel Tout's Anita Calculators web site.

The mid-1970s Adler calculators appear to have been made in Japan from a British design for sale by a German company - but both the British and German companies were owned by Americans! Triumph-Adler was owned by Litton Industries (Monroe) from 1968, and Sumlock (Anita) was owned by Rockwell from 1973.
Adler 108T internal view.
Adler 108T circuit board detail.


Adler 84F Adler Financial Calculator, Model 84F, S/N 68.828.401
Functions: ASMD, percent, financial calculations
Technology: MOS-LSI (Rockwell A4561PB)
Display: 8 digits, vacuum fluorescent module
Dimensions: 75W x 120D x 20H, weight 200g.
Manufactured: Made in Japan for TA Vertriebs GmbH, Nürnberg, Germany, 1975

The Adler 84F is a compact pocket calculator for business and financial applications. In Algebraic mode it performs only ASMD and percentage calculations, with all results rounded to 2 decimal places. In Business mode it performs pre-programmed financial calculations involving prices, payments, and interest, with assistance from the Enter and Compute keys.

The calculator is similar in appearance and construction to the scientific model above, except that the reduced dimensions required the use of smaller AAA batteries. The processor is a single-chip Rockwell A4561PB dated April 1975, on a circuit board labelled "GICO Japan". The display is a 9-digit vacuum fluorescent panel, with the leftmost digit reserved for minus and error indicators. Power consumption is about 400mW.
Adler calculator in slip case.


Novus Mathematician Model 4510 Novus Mathematician, Model 4510, S/N 179491
Functions: ASMD, scientific functions
Technology: MOS-LSI (National MM5760N)
Display: 8 digits, LED module
Dimensions: 75W x 150D x 32H, weight 170g.
Manufactured: National Semiconductor, USA, 1975

The Model 4510 "Mathematician" is one of a family of LED-display calculators manufactured under the Novus brand by National Semiconductor Corporation (NS) in the mid-1970s. (National was and still is a major US manufacturer of analog and digital integrated circuits).

The Mathematician provides trig, log, and power functions, and a single memory register. The "mathematician" label possibly comes from a function to accumulate squares for statistical calculations. Data entry uses the postfix (reverse Polish) system, but the calculator does not use scientific notation. Numbers larger than 8 figures result in overflow, which lights all the zeroes and decimal points. Function calculations are slow, with a busy display and significant errors in the 7th (or sometimes even the 6th) figure. The calculator was no match for the Hewlett-Packard 35, but it was only a fraction of the price, and was still a hundred times more accurate than the slide rule.

The circuitry of the Novus 4510 uses a MM5760N processor and a DM8864 LED driver, with no other components. The calculator draws 20-65mA (600mW max) from a standard 9V battery. A power-saving mode changes the display to all decimal points after about 30 seconds of inactivity.


Qualitron 1438 Conversion Calculator Qualitron Conversion Calculator, Model 1438, S/N 539155
Functions: ASMD, conversion factors
Technology: MOS-LSI (Rockwell A4004PC)
Display: 8 digits, vacuum fluorescent module
Dimensions: 75W x 145D x 35H, weight 250g.
Manufactured: Qualitron, Taiwan, 1975

The Qualitron 1438 is a basic four-function calculator with a range of pre-programmed conversion factors for distance, mass, volume, and temperature. Two slider switches select land or nautical miles, and US or Imperial volumes. There is provision to enter a single user-defined conversion factor.

The conversion operations are very simple: enter the number, press "CONV", select the present unit, then the required unit. For example, to convert 1 pound to grams press 1 CONV lb gram and read the result 453.59236.

The circuit board uses a Rockwell A4004PC processor (no relation to the Intel 4004), an Itron FG95A fluorescent display panel, and a "Best Choice" modular power supply, with only about a dozen discrete components. Power is supplied from four disposable AA batteries, or an external 6V adaptor.

The same machine with different nameplates was also sold as the "Castle Model 1438 Conversion Calculator".
Castle 1438 conversion calculator.
Qualitron and Castle rear nameplates.
Qualitron 1438 circuit board.


Prinztronic SC4001M scientific calculator Prinztronic Scientific Calculator, Model SC4001M , S/N 928647
Functions: ASMD, scientific functions
Technology: MOS-LSI (GI CF-596)
Display: 8 digits, vacuum fluorescent module
Dimensions: 75W x 145D x 35H, weight 250g.
Manufactured: Made in Taiwan, 1975

Prinztronic was the house brand of a British company which sold re-branded calculators from a variety of manufacturers. This Model SC4001M scientific calculator is obviously from the same factory as the Qualitron/Castle shown above.

The scientific functions include exponential notaion, trig functions and their inverses in degrees or radians, natural logs, square roots and reciprocals. There is a single memory register. The calculator operates to 8 significant figures, but displays only 5+2 digits in scientific notation. The trig and log functions are quite slow, and are only accurate to 5 figures. The circuit board is similar to the Qualitron above, but with a General Instruments CF596 processor and a Futaba 9-ST-12 display module.
Prinztronic SC4001M circuit board.


Qualitron 1450 scientific calculator Qualitron Scientific Calculator, Model 1450, S/N 1001516
Functions: ASMD, scientific functions
Technology: MOS-LSI (Rockwell A6500CA)
Display: 8 digits, vacuum fluorescent module
Dimensions: 75W x 145D x 35H, weight 250g.
Manufactured: Qualitron, 1976

The Qualitron 1450 from 1976 appears to be a later and more capable version of the Prinztronic machine above. The 5 memory keys have been reduced to just Store and Recall, and replaced with base-10 logs, powers, and two levels of parentheses.

The circuit board is similar to the two machines above, but with a Rockwell A6500CA processor and a Futaba 9-ST-10 display module. A ribbon cable has been added for the keyboard connection, but there are still plenty of loose flying leads to the switches and power connector. All three machines use the same "Best Choice 4055" modular power supply.
Qualitron 1450 circuit board.


National Semiconductor, Model 200 National Semiconductor, Model 200, S/N 0889-077
Functions: ASMD, percent, square root, 1 memory
Technology: MOS-LSI (National MM57134)
Display: 8 digits, vacuum fluorescent module
Dimensions: 70W x 135D x 15H, weight 160g.
Manufactured: Made in Taiwan for National Semiconductor, USA, 1976

The Model 200 is a basic four-function calculator with percent and square root functions and a single memory register. The casing is only 15mm thick, but this increases to 20mm when enclosed in its imitation-leather wallet. The calculator uses a fluorescent rather than LED display, and carries National Semiconductor's own name rather than the "Novus" brand of their consumer division.

The circuitry consists only of a MM57134 processor, and a modular power supply to drive the Futaba 9-ST-10 display. The calculator draws about 110-130mA (600mW max) from three AAA batteries or an external AC adaptor.


Rockwell Model 18R Rockwell LED Calculator, Model 18R, S/N 354123
Functions: ASMD, percent, 1 memory
Technology: MOS-LSI (Rockwell B5000CC)
Display: 8 digits, NS LED module
Dimensions: 75W x 155D x 22H, weight 160g.
Manufactured: Assembled in Mexico for Rockwell International, Anaheim, CA, 1976

The 18R is one of a family of LED-display calculators produced by Rockwell under their own name in the mid-1970s, shortly before they abandoned the calculator business. The machine illustrated was assembled in Mexico using "US and foreign parts". Others are known to have been assembled in England at the former Sumlock Anita factory.

The circuit board uses a Rockwell B5000CC processor and an 8-digit LED display panel from National Semiconductor. One digit position is sacrificed if a minus sign is required - 0 minus 12345678 gives an error (all decimal points lit) as there is nowhere to show the minus sign. The modular keyboard plugs into the connectors around the right and bottom edges of the circuit board. The calculator draws only 7 to 30mA (270mW max) from a standard 9V battery mounted in the area above the display.
Rockwell 18R circuit board.

Original text and images Copyright © John Wolff 2005-13.
Last Updated: 20 January 2013

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