Hand-held Calculators

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Canon Pocketronic, Pocketronic II,
& Monroe 10

Three very early hand-held calculators from the same stable, with output printed on thermal paper tape.

Canon Pocketronic

Canon Pocketronic
Canon Pocketronic in hand

Canon Pocketronic

Distinctive features: One of the first hand-held, battery-powered calculators.  No display, calculations are printed on thermal paper tape.

Technical details:
Display is by printout on thermal paper tape.


Main integrated circuits - Texas Instruments TMC1730B, TMC1731A, & TMC1732A (here date coded weeks 18 and 19 of 1971) MOS (Metal Oxide Semiconductor) integrated circuits[2].

15.6v (13x NiCd rechargeable cells).

100 mm x 208 mm x 48 mm (4" x 8.2" x 1.9").

Launched in Japan in October 1970[1], and the USA in early 1971[2].

Made in Japan.

Texas Instruments started to investigate the design of a hand-held calculator in 1966 with the "Caltech" project.  This calculator was the resulting commercial product, manufactured by Canon.  Texas Instruments was awarded U.S. and Japanese patents for a "Miniature Electronic Calculator".

At this date there was little choice for the display technology of such a small hand-held calculator:

So, like the prototype Texas Instruments Caltech, the output is printed on thermal paper tape, which was manufactured by 3M[2].  The print head is a 20-segment array where the appropriate segments are heated to 400°F (200C) in 1/100 sec. to produce the required digit on the thermal paper[3]"The developers are aiming the under-$400 unit at the home and small office market"[4].

Canon Pocketronic

Calculator with the thermal tape cartridge removed and a new, sealed cartridge.

Inside Canon Pocketronic

The base of the calculator with covers opened showing the 13 rechargeable cells which are squeezed in.

Inside Canon Pocketronic

Beneath the keyboard showing the printing mechanism and electronics.

Inside Canon Pocketronic

Beneath the keyboard with the printer circuit board removed to reveal the 3 calculating integrated circuits.

Close up of the Texas Instruments TMC1730B, TMC1731A, & TMC1732A integrated circuits, in ceramic packages.

This model was among the first hand-held calculators.

Although it is hand-holdable it is not really a "pocket" calculator due to its great length and thickness (208 mm / 8.2" by 48 mm / 1.9").

It is notable that at this point in the development of calculator electronics that three large-scale integrated circuits (LSI) were required for the calculating functions.

When introduced in 1970 these calculators were at the cutting edge of technology and still having teething troubles.  This is illustrated by a news story in the magazine Electronics in January 1971[5]:
"TI production woes delay calculator
Canon's pocket calculator, which was to be selling in the U.S. last month, is being delayed because production of its thermal print head by Texas Instruments is two months behind schedule.  The calculator, called Pocketronic is designed around three MOS circuits and can add, subtract, multiply, and divide; it was to sell for less than $400.
    TI's James W. Clifton, manager of display products, says he expects to catch up during the second quarter.  The print head, which is used with thermally sensitive paper to provide hard copy readout, is a silicon array of small dots that can be heated in various combinations to form numbers and other characters.  Clifton attributes the delay to the fast turnaround time initially scheduled for the project: 15 months from laboratory to the large-scale production required by the Japanese firm.  The Canon calculator also uses three of TI's MOS/LSI circuits. Apparently, there is no problem in delivering these circuits."


A year or two later Texas Instruments started producing its own range of calculators and sold calculator ICs to many other manufacturers.

Canon Pocketronic II

Canon Pocketronic II

Canon Pocketronic II

Distinctive features: An updated version of the Canon Pocketronic with more integrated electronics, though no smaller and still heavy.  No display, printout on thermal paper tape.
Styling resembles the Monroe 10, below, rather than the original Pocketronic, above.

Technical details:
Display is by printout on thermal paper tape.

Four-function, %.

Main integrated circuits - Texas Instruments TMC0138NC & TMS0641NC (here both are date coded week 29 of 1974).

15v (rechargeable battery pack).

100 mm x 200 mm x 48 mm (4" x 8.2" x 1.9").

Made in Japan.

This calculator is large, heavy, and with output only on the special thermal paper is a bit old-fashioned for the mid- to late-1974 date of when it would have been made, judging by the date codes on the ics.


Inside the Canon Pocketronic II, showing that the higher level of integration of the electronics requires only a single small circuit board.

Circuit board

Close up of the circuit board showing the two Texas Instruments integrated circuits: TMC0138NC & TMS0641NC.

Monroe 10

Monroe 10

Monroe 10, aka "Shrimp"

Distinctive features: Restyled Pocketronic, with styling resemblance to the Pocketronic II, which it preceded.  Labelled by Canon for Monroe, a well-established U.S.A. calculator manufacturer and marketing company.

Technical details:
Main integrated circuits - Texas Instruments TMC1730, TMC1731, & TMC1732 (here date coded weeks 41 and 43 of 1970).

103 x 219 x 43 mm (4.1" x 8.6" x 1.7").

Monroe10 Ad

Advertisement from 1971 for the Monroe 10, here called the "Shrimp".

The cost was "only" US$379.00 (about GBP £160).
According to the U.S. Inflation Calculator the equivalent cost in 2014 would be about US$2,200!




  1. Dentaku Museum site at http://www.dentaku-museum.com/.
  2. "Pocket model", Electronics, Apr. 27 1970.
  3. "Carry This Calculator in Your Pocket", Popular Science, August 1970, p59.
  4. "Totable toter", Electronics, May 11, 1970, p12E.
  5. "TI production woes delay calculator", Electronics, Jan. 4 1971, p17.

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© Text & photographs copyright Nigel Tout   2000-2019  except where noted otherwise.