- A Closer Look at the Compensating Polar Planimeter (Eggers, 2020)
College Mathematics Journal 51:2 (2020): the mathematics of the compensating polar planimeter, showing that averaging pole-left and pole-right readings exactly cancels a misaligned wheel.
- A Contribution to the History of Planimeters (Vossepoel & Zerfowski, 2023)
Slide Rule Gazette 23 (2023): more than 30 lesser-known planimeters of 1814–1884.
- A Treatise on Planimeters: Theory, History and Different Varieties (Frost, 2025)
Lecture slides from the Oughtred Society's 2025 international meeting: the history, theory and many varieties of planimeter.
- American Planimeters (Otnes, 2002)
Journal of the Oughtred Society 11:2 (2002): the planimeters sold in America, K&E's suppliers (Amsler, Coradi, Haff, Ott), and their uses.
- Canon 163 Calculator: Reverse-Engineered Schematic
A 22-page schematic of the Canon 163 Nixie calculator of c. 1968-69, drawn from two working machines: block diagram, timing, the torsional delay line and its amplifiers, TI DTL logic, the 1-2-4-2 serial adder, the multiplexed Nixie display and the +100/+200 V display supplies.
- Canon 163 Calculator: Schematic Appendix
Nine pages of supporting drawings for the Canon 163 schematic: flip-flop forms, timing diagrams, the register and delay-line organisation, state graphs and a worked square root.
- Canon 163 Calculator: Theory of Operation
A 21-page theory of operation written from the reverse-engineered schematic and a logic simulation: the 1 MHz crystal clock, six registers in one delay line, the 1-2-4-2 code, the state machine, number entry, memories, the multiplexed display, and servicing notes (board insertion, forcing states to trace delay-line faults).
- Canon Canola 1200 Logic and Timing Manual
Canon's logic and timing manual for the Canola 1200 Nixie calculator: logic flow, timing diagrams, chip pinouts and schematics.
- Casio 121-B Calculator: Reverse-Engineered Schematic
A 10-page schematic of the Casio 121-B of 1970: Hitachi HD3100 PMOS chips, the NEC uPD116C Nixie decoder-driver, Toshiba high-voltage drivers and multiplexed Hitachi CD-71 Nixies.
- Casio AL-1000 Calculator: Reverse-Engineered Schematic
A 26-page schematic of Casio's programmable AL-1000 of 1967: discrete DTL, core memory for numbers and program, and multiplexed NEC LD-866 Nixies.
- Cathode Ray Tube Phosphors Of Interest To The Experimenter (rev. 20100226)
A compilation of CRT phosphor P-numbers with colour and persistence.
- Compensating Polar Planimeters 4236, 4236M, 4237, 4242 & 4242½ (K&E manual, 1949/1957)
K&E's 32-page manual for its fixed-arm and adjustable compensating polar planimeters, including the 4242½: care, setting up, reading the dial, wheel and vernier, tracing, scale factors, indicator diagrams, pole-inside measurement with the neutral circle, accuracy, the testing rule, tracer-arm settings tables and graph, and the calculus theory.
- Computing Examples for the Curta Calculating Machine
Contina's worked-examples booklet for the Curta: the four basic operations and the short-cut methods built on them, shown step by step with dial settings. Scanned copy; the text layer is OCR and carries errors. Undated; it covers the Model II, so it postdates that model's introduction.
- Curta Calculating Techniques
A loose-leaf set of Curta methods issued free by the British agent, Automatic Business Machines Ltd of London: general techniques, commercial work in sterling, engineering examples, and mathematical procedures such as roots, polynomials and series, with numbered Curta tables. Scanned copy; the text layer is OCR and carries errors. Undated; it covers both models and works in pre-decimal sterling, so it predates February 1971.
- Curta Computing Methods — Business and Statistical Examples, with Five-Place Logarithm Tables
A Curta calculating handbook that opens with a product description and goes on to business methods, statistics on grouped data, and five-place logarithm tables. The scan has a blank cover and no title page, so the title given here is descriptive. The text layer is OCR and carries errors. Undated.
- DE Patent 194,527: Rechenmaschine (C. Hamann, the Gauss)
The modified form of Hamann's round calculating machine, the Gauss, with its setting mechanism arranged radially around a central axis. German twin of US 832,666.
- DE Patent 209,817: Rechenmaschine (C. Hamann, the proportional lever)
Hamann's proportional lever, filed 1906 and published 1909, the mechanism of the Mercedes-Euklid. German twin of US 1,011,617.
- DE Patent 287,770: Rechenmaschine (C. Hamann, Mercedes-Euklid automatic multiplication and division)
Hamann's patent of 1914–15 that gave the Mercedes-Euklid automatic multiplication and division.
- DE Patent 367,726: Rechenmaschine (Deutsche Telephonwerke, the switching latch)
The first switching-latch patent, filed 24 October 1920 and published 25 January 1923: gear wheels engaged by a latch for a number of teeth set by a stationary disk, instead of pinwheels, with the tens carry made by the drum itself.
- DE Patent 384,150: Rechenmaschine (Deutsche Telephonwerke, one wheel per place)
Filed 24 February 1923: the one-wheel-per-place switching latch, with internal and external teeth on each wheel, the fixed disk and settable segment that form the latch's track, anti-overrun locks and the setting indicator.
- DE Patent 432,435: Rechenmaschine (Deutsche Telephonwerke, automatic division)
Filed 19 December 1924: automatic division with the crank turning one way for every operation, by a reversing gear and a half-step carriage movement. German twin of US 1,788,192.
- DE Patent 443,479: Rechenmaschine (Deutsche Telephonwerke, reversible revolutions counter)
Filed 4 March 1926: the reversible revolutions counter, with the counter lever's + and − positions holding the two-armed counting finger on one side or the other.
- DE Patent 468,275: Rechenmaschine (Deutsche Telephonwerke, counter tens carry)
Filed 4 March 1926: the tens carry for the revolutions counter, the change from the Manus A to the B.
- DE Patent 748,500: Rechenmaschine (C. Hamann, back-transfer)
Hamann's 1940 back-transfer patent, carrying a result back into the setting levers.
- DE Patent 88,223: Führung der Mess- oder Zählrolle an Instrumenten (C. Hamann, planimeter)
Hamann's patent of 11 June 1895, from his instrument workshop in Friedenau, Berlin: a guide for the measuring wheel of planimeters and integrators, using an isosceles slider-crank in place of the Amsler polar or Wetli linear mechanisms.
- DE Patent 919,787: Rechenmaschine (C. Hamann, back-transfer of the Manus R)
Christel Hamann's last major patent, filed 29 October 1949: the back-transfer device of the Manus R.
- Die Klassifizierung mechanischer Rechenmaschinen, Teil 3: Schaltwerksprinzipien
Haertel's classification of the actuating mechanisms of mechanical calculators (3rd ed., in German): stepped drum, pinwheel, proportional lever, switching latch and the rest, crediting Christel Hamann with the switching latch.
- Die Planimeter: deren Theorie, Praxis und Geschichte (Trunk, 1865)
A German history and theory of the planimeters known by 1865, from Hermann and Oppikofer to Amsler.
- Friden 1162 Logic Schematic
The logic-level schematic of the integrated-circuit Friden 1162.
- Friden 130 Electronic Calculator Instruction Manual
The 52-page operator's manual for the EC-130: the keyboard, the four-register stack, ENTER and REPEAT, decimal setting, and worked examples.
- Friden 130 Electronic Calculator Sales Brochure (1964)
The six-page launch brochure: the CRT showing four registers, the 11-key keyboard, "no moving parts".
- Friden Calculator Projects 1961-1968
Friden's internal list of calculator development projects from 1961 to 1968.
- Friden Calculator Projects 1961-1979
Friden's list of calculator projects from 1961 to 1979, including the Hitachi-built EC-111x Nixie line.
- Friden EC-130 Field Service Manual (August 1964)
The 51-page field service manual issued at the EC-130's launch: installation, adjustments, fault finding and parts.
- Friden EC-130 Logic Schematic, Four-Counter (Fall 1964)
The one-sheet logic-level schematic of the four-counter EC-130: every gate and flip-flop, without the power supply, delay-line read/write electronics or CRT drive.
- Friden EC-130 Logic Schematic, Three-Counter (late 1965)
The logic-level schematic of the three-counter EC-130.
- Friden EC-130 Master Design Documentation Computer Printout (1964)
Friden's internal Master Design Documentation printout for the four-counter EC-130, version 1: the machine's logic equations as a computer listing.
- Friden EC-130 Service Manual (September 1965)
The 161-page factory service manual for the four-counter EC-130: theory of operation down to gate level, the delay line and its amplifiers, the counters, every keyboard function as a flow chart, the display circuits (segment, dot and staircase generators, slant and deflection amplifiers, diode matrix), the power supplies including the -2,400 V multiplier, and adjustment procedures.
- Friden EC-130 Three-Counter Service Manual Supplement (December 1965)
The 26-page supplement covering the three-counter EC-130 (serial 8501 on), which drops the B counter.
- Friden EC-130/EC-132 Service Letters #1-#35 (1964-1968)
The factory service letters for the 130 and 132, from July 1964 to June 1968: field changes, fault fixes and production changes, including the three-counter change.
- Friden EC-132 Logic Schematic (June 1965)
The logic-level schematic of the EC-132, including the square-root logic.
- Friden EC-132 Master Design Documentation Computer Printout (June 1965)
Friden's internal Master Design Documentation printout for the four-counter EC-132.
- Friden EC-132 Temporary Service Manual (August 1965)
The interim service manual for the EC-132.
- Friden EC-132 Temporary Service Manual: Square Root Mathematics (1965)
How the EC-132 extracts a square root by subtracting successive odd numbers, for service technicians.
- Friden Final Engineering Report: Magnetostrictive Delay Line (June 1964)
Friden's 48-page engineering report on the EC-130 delay line: the Ni-Span C wire, the transducers, the mounting and the measured performance.
- Friden Report on the Victor 3900 (1965)
A 1965 Friden competitive report concerning the Victor 3900 MOS calculator, held by the Old Calculator Web Museum.
- Generating Characters (Electronics, 3 January 1958)
The MIT Lincoln Laboratory article on drawing characters on a CRT from sine and cosine waveforms, the method behind the Wyle Scientific's display.
- Geometry of the Prytz Planimeter (Foote)
The mathematics of the hatchet (Prytz) planimeter.
- Haff Planimeters 313, 315 and 317: Instruction Manual
The current manual for Haff's compensating polar planimeters, worded almost exactly like K&E's 1957 manual, with the 200 sq in / 2000 sq cm constant circle.
- Handhabung der Hamann Manus R Rechenmaschine (1953)
The factory operating manual for the Manus R, in German, including the back-transfer lever the R added.
- Handhabung der Hamann Manus Rechenmaschine
The factory operating manual for the Manus (a model D is pictured), in German: the controls, addition, subtraction, multiplication and automatic division, with the numbered control map.
- Hewlett-Packard Journal, September 1968: the HP 9100A
The HP Journal issue introducing the 9100A: Osborne on the hardware (CRT display, inductive printed-circuit ROM, core-rope control ROM, core memory), Cochran on the internal programming (number representation, CORDIC-style trigonometry, logarithms), Monnier and Near.
- Historie Diehl: Elektronische Rechner
Pages from Diehl's company history on its electronic calculators, including the Combitron of 1966 (in German).
- Hitachi HD3100 Series PMOS Calculator IC Data Sheets
Data sheets for Hitachi's HD3100-series PMOS chips used in the Friden EC-1114/1115, Casio 121-B and other Japanese Nixie calculators: shift registers, gates, flip-flops and the serial adder.
- HP 9100A Calculator Brochure (1968)
Hewlett-Packard's launch brochure for the 9100A.
- HP 9100A Operating and Programming Manual
The owner's manual for the 9100A (09100-90001): the keyboard, the X, Y, Z display registers, storage registers, programming and magnetic cards.
- HP 9100A Training Manual
Hewlett-Packard's training manual for the 9100A.
- HP 9100A: Trinity College Dublin Computer Collection Catalogue Entry
A detailed catalogue entry on the 9100A: board list, control and program ROMs, microword format, core memory and internal photographs.
- HP 9100B Microprogram Flowcharts
The algorithmic-state-machine flowcharts of the 9100B's microprogram: the nearest thing to its ROM listing in public.
- HP 9100B Operating and Programming Manual
The owner's manual for the 9100B (09100-90021), with its doubled memory and subroutines.
- HP 9100B Program Library (1969)
HP's library of 9100B programs for science, engineering, statistics and finance.
- HP 9100B Schematics
Factory schematic sheets for the HP 9100B: logic boards, flip-flop boards, side-board expanders, card reader and supplies.
- HP 9125A Plotter Service Manual (1970)
The service manual for the 9125A X-Y plotter used with the 9100.
- HP 9160A Marked Card Reader Operating Manual (1969)
The operating manual for the 9160A card reader peripheral of the 9100.
- IME 26 Instruction Manual
The instruction manual for the IME 26 commercial calculator: keyboard, registers, basic operations, constants, chain calculations and worked commercial examples.
- IME 84 Calculator: Reverse-Engineered Schematic
A 26-page schematic of the IME 84 of 1964: germanium DTL, core memory, decade counters and the 16-digit multiplexed Nixie display, with a board list (408 transistors, 1,045 diodes).
- IME 84 Calculator: Theory of Operation
A 33-page theory of operation of the IME 84: the 20 kHz clock and digit cycle, core read and write, decade-counter arithmetic, the procedures for each key, and notes on replacing germanium parts (BAT46, 2N3906, MPSA92).
- IME 86S Calculator: Reverse-Engineered Schematic
A 27-page schematic of the IME 86S, the IME 84's successor: discrete germanium logic, core memory and Nixie display.
- IME 86S Calculator: Theory of Operation
A 34-page theory of operation of the IME 86S, written from the reverse-engineered schematic.
- Lightning Calculator: Collection Record (FAU ISER)
The Erlangen computer-science collection's record of a Grand Rapids Lightning D-3 on its wooden base: 7 digits, 33 × 9 × 5 cm, 720 g with the stand.
- Mechanical Integrators, Including the Various Forms of Planimeters (Shaw, 1886)
Hele Shaw's survey of planimeters and integrators of every kind known in 1886, with their theory.
- Modern Electronic Package for the Wang 300 Series Consoles: Manual
Bob Alexander's manual for his PIC32 board that brings a Wang 300 keyboard console to life without the original electronic package: installation, keyboard and Nixie testing, cathode poisoning, the Wang emulation, a GPS clock and an RPN calculator.
- Monroe 920 Service Manual
The 116-page service manual for the Monroe 920 electronic calculator.
- Monroe 925 Calculator: Reverse-Engineered Schematic
A 17-page schematic of the Monroe 925 of 1970, with delay-line memory and multiplexed JRC B-5755 Nixies.
- Monroe 925 Logic and Timing Manual
Monroe's logic and timing manual for the 925 Nixie calculator.
- Olympia RAE 4/15-2: Collection Data Sheet
The FAU Erlangen collection record for an Olympia RAE 4/15-2 electronic calculator of 1964, with 15 Nixie tubes.
- Operating the Hamann Manus Calculator (English translation)
An English translation of the DeTeWe Manus manual by Knut Faegri Jr., with Steven L. Carter, Heinz Schneemann and Christian Hamann.
- Reparaturanleitung Hamann Automat S
The factory repair manual for the Automat S, in German, 29 pages: the switching-latch drum, adjustments, a fault table and service figures. The drum is the same mechanism as the Manus's, so it is the nearest thing to a Manus repair manual.
- Russian Nixie Tube Data Sheets (compilation)
A compilation of data sheets for Soviet IN-series Nixie tubes, from Dieter Waechter's tube archive.
- Sharp Compet 17 Calculator: Reverse-Engineered Schematic
A 17-page schematic of the Sharp Compet 17 of 1968: MSI MOS logic and multiplexed Hitachi CD-81 Nixies.
- Singer Friden 1115 Electronic Calculator Service Manual (December 1969)
The service manual for the EC-1115: specifications, key functions, worked calculating methods, the Hitachi HD3100 chips, register operation, the anode charge-pump and cathode control circuits of the 12-tube Nixie display, power supply, troubleshooting and flow charts.
- Singer Friden EC-1113 Service Manual (June 1969)
The 132-page service manual for the Hitachi-built EC-1113, with 108 HD700 PMOS chips and 12 Hitachi Nixies; some pages missing.
- Sony SOBAX 2500 Calculator: Reverse-Engineered Schematic
A 27-page schematic of the programmable Sony SOBAX 2500 of 1969-70: the 362 cm longitudinal delay line, the phase-locked master clock, Sony 500-series logic and the multiplexed Hitachi CD-81 Nixie display.
- Sony SOBAX 2500 Calculator: Schematic Appendix
Eleven pages of supporting drawings for the Sony 2500 schematic: timing, register maps and state diagrams.
- Sony SOBAX 2500 Calculator: Theory of Operation
A 52-page theory of operation: the delay line time-multiplexed into 16 channels, the PLL clock locked to the line, the 1-2-4-2 serial arithmetic, programming, the display latch, zero blanking and thousands separators.
- The Curta, a Technical Marvel
Herbert Bruderer's 2022 article on Curt Herzstark and the Curta, its manufacture in Liechtenstein, and what newly found patent documents and design drawings show about the Multiple Curta, a parallel calculator.
- The Lightning Calculator: Bonham, Hook and Pangborn
Otnes's history of the Lightning and its makers, from Grand Rapids and Los Angeles city directories, with photographs and X-rays of the machines. Journal of the Oughtred Society 11:1 (Spring 2002), pp. 53–58.
- The Polar Planimeter and Its Use in Engineering Calculations (Wheatley, 1903)
K&E's book on the polar planimeter: its theory, the zero circle, and its use for indicator diagrams, earthwork, reservoirs and other engineering calculations.
- The Polar Planimeter of Jakob Amsler (van der Salm)
A history and vector-analytic treatment of Amsler's polar planimeter and its precursors.
- Tom Osborne's Story: the Green Machine and the HP 9100
Osborne's own account, written to Barney Oliver, of designing the Green Machine prototype and the HP 9100A.
- Toshiba BC-1212 Calculator: Reverse-Engineered Schematic
A 17-page schematic with state diagram of the Toshiba BC-1212 of 1970: MSI MOS logic and multiplexed NEC LD-955A Nixies, including the under-rated 0.022 uF digit-driver capacitors.
- Tractrices, Bicycle Tire Tracks, Hatchet Planimeters, and a 100-year-old Conjecture (2013)
American Mathematical Monthly 120 (2013): the hatchet planimeter and its connection with bicycle tracks.
- US Design Patent D163,135: Pocket Adding Apparatus (K. R. Pangburn)
Design patent of 1 May 1951 for Pangburn's pocket adder, whose mechanism is virtually identical to the Lightning's.
- US Design Patent D163,136: Pocket Adding Apparatus Unit (K. R. Pangburn)
The companion design patent of 1 May 1951 for Pangburn's pocket adder.
- US Patent 1,011,617: Calculating-Machine (C. Hamann, the proportional lever)
Hamann's proportional lever for the Mercedes-Euklid, filed 28 June 1910 and granted 12 December 1911 (DE 209,817).
- US Patent 1,410,507: Calculating Machine (W. T. Ray)
Ray's stylus calculating machine, granted 21 March 1922, one of the dial adders related to the Lightning.
- US Patent 1,574,249: Adding Machine (R. W. Hook, the Lightning)
Hook's patent for the Lightning Adding Machine, filed 17 February 1921 and granted 23 February 1926: the actuators, numeral wheels, long carry tooth and weighted pawls of the stylus dial adder. The Dial-Adders theory volume uses its part numbers.
- US Patent 1,764,915: Calculating Apparatus (A. E. Vethe, the Addometer)
Vethe's Addometer patent, filed 10 September 1928 and granted 17 June 1930.
- US Patent 1,788,192: Computing Machine (C. Hamann, the Manus switching latch)
Hamann's switching-latch calculator with automatic division, filed 17 December 1925 and granted 6 January 1931; the US twin of DE 432,435. The Manus theory volume uses its part numbers.
- US Patent 1,829,379: Computing Machine (A. E. Vethe, the Addometer)
Vethe's computing-machine patent, filed in Oslo on 20 October 1926 and granted 27 October 1931.
- US Patent 1,940,069: Calculating Machine (J. H. Bair)
The Bair / Bair-Fulton adder, granted 19 December 1933: "essentially a Kummer" with an assisted manual carry, a borderline member of the stylus dial-adder type.
- US Patent 1,968,201: Calculating Machine (C. Hamann, the Automat)
Hamann's electric switching-latch machine with automatic multiplication, granted 31 July 1934.
- US Patent 2,450,668: Calculator (E. G. Kesling, the Kes-Add)
Kesling's pocket dial adder, filed 22 May 1944 and granted 5 October 1948.
- US Patent 2,797,047: Calculator (O. Lehre, the Dial-A-Matic)
Lehre's Dial-A-Matic, granted 25 June 1957.
- US Patent 2,874,320: Indicating Device (H. J. Hampel, Burroughs Nixie)
The Burroughs stacked-cathode indicator tube, filed 13 December 1955 and granted 17 February 1959: photo-etched character cathodes, offset stacking for wide viewing, insulating light-absorbing rear coatings.
- US Patent 2,935,257: Releasable Restraining Device for Rotatable Parts of Calculators (E. G. Kesling)
Kesling's later patent for his pocket dial adder, filed 26 January 1955 and granted 3 May 1960.
- US Patent 3,280,315: Key Controlled Decimal Electronic Calculating Machine (N. Kitz, Bell Punch, ANITA)
Kitz's ANITA patent, filed 29 December 1961 (priority 1957) and granted 18 October 1966: decade counting devices, nines-complement subtraction, multiplication by repeated addition and shifting, division by repeated subtraction, and an early brush-scanned version with numeral wheels.
- US Patent 3,305,843: Display Apparatus (T. J. Scuitto, Wyle Laboratories)
The Wyle Scientific display, filed 16 December 1963 and granted 21 February 1967: digits drawn from gated sine and cosine arcs, timed from a cyclic memory.
- US Patent 3,388,384: Zero Suppression Circuit (General Micro-electronics, Victor 3900)
The Victor 3900's leading-zero suppression for its CRT display.
- US Patent 3,402,285: Calculating Apparatus (An Wang, logarithms)
Wang's logarithm method, filed 22 September 1964 and granted 17 September 1968: stored logs of 10, 2, 0.9, 1.01, 0.999 and 1.0001, factors of the form 1 +/- 10^-n applied by shift and add, with worked tables for ln 2.10 and the antilog of 4.23845.
- US Patent 3,430,095: Cathode Ray Tube Beam Positioning System Employing Composite Signals (Friden)
The SRI-developed Friden display, filed 8 July 1965 and granted 25 February 1969: staircase generators for position, a segment counter, weighted stroke origins and an oscillator sweep for the strokes.
- US Patent 3,453,601: Two Speed Arithmetic Calculator (Bogert and Miner, Victor 3900)
The Victor 3900's MOS calculator, running at 330 kHz to compute and 60 kHz to display, with stroke-drawn figure-8 digits.
- US Patent 3,454,785: Shift Register Employing Insulated Gate Field Effect Transistors (Norman, GME)
General Micro-electronics' dynamic MOS shift register, the memory of the Victor 3900.
- US Patent 3,518,629: Recirculating Memory Timing (S. P. Frankel, Computron / SCM Cogito)
Frankel's recirculating-memory timing, from the design line that became the SCM Cogito 240.
- US Patent 3,523,282: Calculator (R. A. Ragen, Friden)
A second Ragen calculator patent, filed 24 September 1964 and granted 4 August 1970.
- US Patent 3,526,760: Square Root (R. A. Ragen, Friden EC-132)
The EC-132's square-root method by subtraction of successive odd numbers, filed 1 April 1966 and granted 1 September 1970.
- US Patent 3,546,676: Calculator (R. A. Ragen, Friden)
Ragen's master patent for the Friden electronic calculator, filed 29 October 1963 and granted 8 December 1970: recirculating memory, single-digit counters, the CRT display. Hundreds of drawing sheets.
- US Patent 3,566,160: Simplified Race-Preventing Flip-Flop (T. E. Osborne, HP)
The J-K flip-flop with selectable noise immunity used throughout the HP 9100.
- US Patent 3,588,873: Information Display Apparatus (Osborne, Magleby, Lukes, HP)
The HP 9100 display, filed 12 November 1968 and granted 28 June 1971: figure-8 characters from E- and I-shaped sweeps, narrow-character centring, grouping in threes, mains-locked refresh.
- US Patent 3,623,156: Calculator Employing Multiple Registers and Feedback Paths (T. E. Osborne, HP)
Osborne's calculator architecture patent behind the 9100: power gating, subroutine control and the integrated CRT pattern.
- US Patent 3,634,666: Electronic Desk Top Calculator Having a Delay Line and Automatic Decimal Alignment (Friden)
A division of Ragen's master patent: the delay-line organisation, register roles and automatic decimal alignment.
- US Patent 3,654,612: Display System Using a Cathode-Ray Tube (Takachiho Koheki, Descal)
The Descal ASI-500 display: slope and step sweeps with a ROM blanking the unused parts of each digit.
- US Patent 3,778,778: Calculator with Self-Synchronous Recirculating Memory (Friden)
The delay-line timing of the Friden calculators: a gated clock resynchronised by a sync pulse on every pass, the 16-column, 6-register, 16-bit data train, and pulse-count digits.
- US Patent 414,959: Adding Machine (C. H. Webb, improved)
Webb's improved adder, filed 28 April 1888 and granted 12 November 1889.
- US Patent 689,255: Adding-Machine (J. J. Walsh, the Calcumeter)
Walsh's Calcumeter, filed 16 January 1901 and granted 17 December 1901: a straight row of identical stylus dials with a latch carry, the first commercial success of the type.
- US Patent 75,322: Improvement in Adding-Machines (C. H. Webb)
Webb's adder of 10 March 1868: two concentric stylus wheels, 00 to 99 and hundreds. The first dial adder to sell in quantity in America.
- US Patent 832,666: Calculating-Machine (C. Hamann, the Gauss)
Hamann's round calculating machine, the Gauss, filed 28 March 1905 and granted 9 October 1906 (DE 194,527).
- US Patent 845,747: Calculating-Machine (W. R. Bonham)
Bonham's stylus dial adder, filed 20 November 1905 and granted 5 March 1907: a row of dials with two reversed rings of numerals for adding and subtracting. The Lightning's direct ancestor.
- US Patent 897,688: Resetting Device for Adding-Machines (J. J. Walsh)
The Calcumeter's reset wheel, filed 29 November 1907 and granted 1 September 1908.
- US Patent 908,731: Calculating-Machine (W. R. Bonham, carrier-disk carry)
Bonham's second patent, filed 6 April 1905 and granted 5 January 1909: the carrier-disk tens carry between the stylus dials.
- Wang 300 Series Electronic Calculator Instruction Manual, Volume 1 (1968)
The 84-page operator's manual for the Wang 300, 310, 320, 360 and 362: installation, the work register, two adders and log register, every key with worked examples, accumulator switches, storage registers, trigonometric keyboards, card programming and the item counter.
- Wang 320K Keyboard/Display Unit: Reverse-Engineered Schematic
A 3-page schematic of the Wang 320K keyboard and display unit of the Wang 300 series: the key encoder, the diode-matrix Nixie decoder, cathode and anode drivers on +250 V, and the connector pinouts to the electronic package.
- Wang 500 Schematic
Factory schematics of the Wang 500 programmable calculator.
- Wang 700 A/B Manual
The 96-page manual for the programmable Wang 700A and 700B calculators.
- Wang 720A/B Reference Manual (1970)
The reference manual for the programmable Wang 720A and 720B, with Nixie display.
- Wang Laboratories Catalog and Price List (November 1968)
Wang's product catalogue and price list of November 1968: the 300 series packages and keyboards, programmers, the 700-series precursors, peripherals and prices.
- Wang LOCI Service Manual
The factory service manual for the Wang LOCI logarithmic calculators: logic, timing, the core store, power supply and maintenance.
- Wang LOCI-2 Reference Manual (December 1966)
The 108-page LOCI-2 reference manual: the W, A and L registers, logarithmic multiplication and division, storage registers, the program counter and card programs, decisions, loops, subroutines, Newton's method, and diagnostics.
- Wyle Scientific Instruction Manual (1964)
The 20-page operating manual for the Wyle WS-01/WS-02 Scientific: registers, functions, and the optional PC-01 punched-card reader.
- Your CURTA Calculator
The Curta operating instructions for Models I and II: handling, the four operations, and care. This is a retyped edition of Contina's printed manual, transcribed by Rick Furr in 1997 and reformatted as a PDF by Daniel Ford in 2005, so its page layout is not the original's.
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