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Mathatronics Mathatron 8-48M Mod II Electronic Calculator

Updated 2/26/2017

The Mathatronics Mathatron electronic calculator is a very historic machine, marking many firsts in the electronic calculator industry. While generally overlooked by history, the machines made by Mathatronics were way ahead of their time, offering features that in many cases were not available from other calculator makers for years. While this exhibit is related to the Mathatronics 8-48M Version II, which was introduced a little over a year after the formal introduction of the original Mathatron 4-24 calculator, the exhibit attempts to capture as much as is known of the history of Mathatronics, and the development of their amazing calculators.

The Mathatron calculators underwent a great deal of change early in their lifetime, with the company introducing variations based on improvements in design and capability in rapid-fire succession. Some of the timeline is difficult to track due to a lack of definitive information, however, some history has been able to be recovered through discussions with one of the founders of the company, and also from vintage articles and advertising that has been found.

The first Mathatron calculator was the Model 4-24. This designation was due to the fact that the machine had four memory registers, and 24 steps of learn-mode program memory. This machine had two rotary switches on its front panel; one acting as the power switch, and the other to select the operating mode of the machine. The 4-24 was soon joined by a machine with expanded memory, designated the Model 8-48, which doubled the memory register and program step capacity. Both of these machines were four function (addition, subtraction, multiplication, and division) machines, using fully algebraic problem entry that followed the rules of arithmetic precedence, provided store/recall memory registers, and also was capable of learn-mode programming, which allowed the calculator to "learn" sequences of key-presses, then replay them to automate calculations.

Keyboard of the Mathatron 8-48 Mod II

The Model 8-48M Version II is an improvement over the original Version I Mathatron calculators, by virtue of a redesign that made a few changes to the machine. The first change was that the original versions of the machines used rotary switches for the power switch and mode-selection function of the calculator, while the the Version II machines changed these controls to pushbutton switches. The power switch became a push-on/ push-off pushbutton, and the operating mode of the calculator switched to a group of four pushbuttons, which were set up such that only one of them (LEARN, NORMAL, BRANCH, and STOP) could be depressed at any one time (pressing one that wasn't depressed would cause the existing button that was depressed to pop up to its non-depressed state). The first version of the 8-48M shared essentially the same "CPU" (main logic assembly) with the original Mathatron 8-48, with additional logic to provide the pre-programmed functions, which were selected by yet another rotary switch on the front panel that selected which higher-level math function was to be performed when the nearby [ENTER] button was pressed. The Version II 8-48M utilized the "Model II" logic unit, which incorporated some design changes to the logic unit to better integrate the pre-programmed functions into the operation of he machine, providing single key access (via an additional bank of up to twelve keys to the right of the math function keys) to these functions rather than selection by a rotary switch.

Actual "ticker-tape" printout from Mathatronics Mathatron calculator

The pre-programmed functions of the 8-48M were stored in a magnetic core read only memory (ROM), holding program steps which would carry out the various functions. Because the ROM could hold a selection of programs for any type of calculation, there were a number of different models (both versions I and II) with ROM programs that were targeted toward various specialized math applications. The 8-48M was targeted toward mathematical applications. The model 8-48S had pre-programmed functions applicable to statistics work. The model 8-48C provided pre-programmed functions for civil engineering calculations, and lastly, the model 8-48SC provided functions useful for scientific calculations.

The Mathatronics Mathatron calculators hold a very important place in electronic calculator history. When introduced in late 1963, the Mathatron was the first solid-state, monolithic, desktop, printing, floating point, algebraic entry, user-programmable, stored-program electronic calculator. That's quite a mouthful, but these dramatic (for the time) distinctions make the Mathatron the first production example of a desktop "personal computer" that could be programmed to automatically carry out complex calculations. Olivetti's Programma 101 is historically recognized as being the first desktop "personal computer", but the Mathatron was shipped to its first paying customer (Woods Hole Oceanographic Institute) nearly a year before the Programma 101 was announced. The Olivetti machine can boast an important first, that of providing for offline storage of programs and data via a recordable magnetic card -- a feature that made it possible to quickly change the program in the machine without having to type it in each time. This first, combined with Olivetti's already solid position in the business machine marketplace, allowed Olivetti's machine to receive more attention than the Mathatron, which cemented its place historically, even though the Mathatron was truly the first of its kind.

The idea for the Mathatron was the brainchild of William Kahn, an electronics engineer who was frustrated by having to work with the slow and cumbersome electro-mechanical Friden, Marchant, and Monroe calculators of the day. Having worked on the design of first and second-generation computers at Datamatic (Honeywell's computer division), Kahn felt that many of the concepts of large computers could be scaled down to a small desktop-sized "personal" machine that would dramatically increase the productivity of people involved with performing complex mathematical operations as part of their daily work. Kahn worked in his spare time developing the ideas behind such a machine. After finishing up the design for Honeywell's H-800 computer, Kahn left Honeywell to go to work for Raytheon. Kahn had shared his ideas for a calculating machine with his former boss at Datamatic, Roy Reach, who seemed intrigued with Kahn's vision of a personal desktop "computer". At Raytheon, Kahn met David Shapiro, who also shared enthusiasm for Kahn's ideas. A lot of discussions ensued, and in February of 1962, the three men quit their jobs, and set out on their own to form a company with the goal being to make Kahn's concept into a commercial reality. The men pooled their own money to come up with $18,000 of startup funding, and managed to round up an additional $54,000 in capital from outside investors. Roy Reach's wife, Marjorie, came up with the name for the calculator -- "Mathatron". This served as the root of the name of the company, Mathatronics, Inc. The men set up shop in Waltham, Massachusetts, and used the initial funding to create a working prototype of the calculator. The initial purpose of the prototype was to demonstrate that e the concepts of the calculator were sound and able to be implemented in transistorized hardware to Mathatronics' outside investors, who were granted options in the company shortly after it was formed. These options would mature and become actual shares in the ownership of Mathatronics thirty days after the first successful demonstration of the prototype to the investors. At that point the investors could exercise the options and purchase their shares, providing the company the next infusion of capital it needed to to turn the prototype into a production product. Thus, everything depended on the prototype machine did all it was promised to be able to do, and it must do so in a clearly demonstrable fashion.

"Clamshell" design of the 8-48M Version II, logic unit on bottom, keyboard/magnetic core/power supply in the upper part of the cabinet

Kahn, Reach, and Shapiro worked tirelessly (and without pay) through late 1962 to design the logic of the machine, then take the circuit designs and construct and test the various logic functions, then connecting everything together to construct the working prototype. In early December, 1962, their genius and hard work was rewarded in the form of an operating prototype calculator that met the requirements stated to the investors. This prototype machine had the basic form factor and features of the production calculator, but was housed in a wooden cabinet, that was a bit larger in dimensions than the production calculator, as for the purposes of the prototype, more space was needed to allow for easy access to the circuitry for diagnostics and testing purposes. Once the design was committed to production, the spacing between components and use of printed circuit boards rather than hand-wired prototype boards would allow the machine to shrink in size. The prototype provided four memory registers and 24 steps of program storage. The machine had decision-making features, allowing conditional and unconditional branching, making iterative calculations feasible. It provided printed output in the form of a fast 'ticker-tape' style serial impact printer. It had a capacity of nine significant digits, with full floating decimal, and a two digit decimal exponent ranging from 10-42 to 10+58. The machine featured full algebraic entry, meaning that problems would be entered on the keyboard just as they would be written on paper, with the machine following the mathematical rules of precedence and obeying parentheses. The calculator automatically performed the four standard math functions quickly and accurately, printing out the results nearly as fast as problems could be entered into the machine. No other desktop electronic calculating machine on the planet at the time could even begin to compare to the capabilities of the prototype Mathatron. In some cases, the features that the prototype (and production) Mathatron calculators provided would not be available in a stand-alone desktop electronic calculator for years to come.

The prototype machine, designated the Mathatronics Mathatron Model 4-24 (for the four memory registers, and 24 steps of program memory), was successfully demonstrated to the group of of initial investors a few weeks after it was fully functional and well tested, in late December of 1962. To say that the investors were spellbound by the demonstration was an understatement, and everyone quickly stated they wanted to buy up their options in the company, raising an additional $300,000 of capital which would be used to develop a production-ready version of the prototype as well as build out the infrastructure to build the machines, market them, sell them, and provide post-sales support.

In early 1963, Roy Reach started touring around the US with a non-functional wooden mockup that represented what the production calculator was anticipated to look like, painted up in the company color scheme (an almost IBM-ish blue). Along with the mockup, he also brought along and examples of printed output from the prototype calculator, showing the ease with which it could plow through complex calculations with the user simply entering the equations as they would be written on paper, without having to go through any mental gymnastics to translate the problem into a form that the machine could digest. While Reach was on the road, Kahn and Shapiro were hard at work creating the the first production version of the calculator and preparing the construction documentation so that the machines could be built by a team of experienced electronics assemblers that would soon be hired by the company.

One of the places that Reach visited fairly early in his travels was Woods Hole Oceanographic Institution (WHOI). Based on the virtues of the paper tape output from the prototype machine, along with Reach's convincing sales pitch, WHOI placed orders for two Mathatron 8-48 (double the memory and program step capacity of the prototype machine), without ever seeing a real calculator. They were so enthused about the prospect of being able to put a programmable "computer" on board their research vessels that could be used for all kinds of data reduction and quick analysis of scientific data gathered during their research at sea, that they were willing to order two loaded Mathatrons without ever having seen a real example of the machine.

At the time that the WHOI orders were placed, a lot of details had yet to be worked out for the actual production calculator. WHOI wasn't daunted by having to wait for a production machine, as the calculator was exactly what they needed for ship-board calculations for their oceanographic research. At the time, there simply wasn't anything else in existence that could come close to the capabilities of the Mathatron that would also fit within the limited confines of a sea-going research vessel.

Mathatron 8-48M Version 2 "Top Plate Assembly"
Left: Keyboard Encoder
Right: Core Memory Arrays

In June of 1963, Friden had publicly demonstrated their groundbreaking solid-state calculator, the Friden 130. The Model 130 is historically recognized as the first desktop solid-state electronic calculator. While a major accomplishment, the features of the Friden 130 paled in comparison to the capabilities of Mathatronics' calculators. And, at around the same time of the Friden 130's debut, Mathatronics had production Mathatron 8-48 calculators ready to deliver to WHOI.a The first production machine had gone through a bunch of testing to make sure that it worked properly, delivering accurate answers to every possible problem submitted to it. By the time it came to deliver this "Job 1" machine, the team was convinced it was ready for the customer.

Kahn and another Mathatronics engineer named Charles French loaded the very first production Mathatron 8-48 calculator, which had been promised to WHOI, into Kahn's car, and set out for the roughly 90 minute drive to WHOI. They were enthusiastically greeted by their hosts from WHOI, who helped them carefully unload the precious calculator from Kahn's car, and move it it into the building, where it was set up in a conference room with quite a few people eagerly waiting for the demonstration of this amazing new technology. Unfortunately, when the machine was powered up for the scientists at WHOI, it did not operate properly! It was immediately assumed that something was amiss due to the vibration the machine experienced during the drive to WHOI, so some quick attempts were made to identify any kind of loose connection that might explain why the machine was not operating properly, but nothing was obvious, and the demonstration had to be scrubbed. Feeling rather frustrated, Kahn and French loaded the machine back into the car, and made what felt like a much longer drive back to Waltham, determined to figure out what had gone wrong. A couple of weeks later, the issues had been identified and fixed, and some changes incorporated into the production design so that similar problems would not occur on subsequently built calculators. The changes were incorporated into machines already being built, requiring rework on the machines in process, which delayed their delivery a bit. In early July of 1963, Kahn and French returned to WHOI with a fully operating machine. The folks at WHOI were enormously satisfied with the machine, and immediately made arrangements for the machine to be installed on-board one of their research vessels that was in port at the time. Shortly thereafter, the #2 production Mathatron 8-48 calculator was delivered to WHOI, where it was sent by helicopter to meet up with the same research vessel, which had set to sea by then.

Keyboard implementation detail: Key cap actuated micro-switches

Technically, it could be argued that the Mathatronics Mathatron calculator should take the historical credit from Friden as being the first solid-state desktop electronic calculator, but the Mathatron was not publicly introduced until November, '63 while Friden's EC-130 was introduced in June. Both Friden and Mathatronics (as well as a few other companies) had prototype calculators running in late '62, but from a historical perspective, the formal public introduction of a calculator for sale seems to be the appropriate benchmark to use for determining who was first to market with a new technology.

At the same time that Mathatronics was working to get the WHOI order fulfilled, manufacturing capacity had ramped up, but the marketing effort had stalled a bit. There were a few orders that had come in from other customers that had been visited by Roy Reach during his initial drive-about marketing campaign ( among them, orders from MITRE Corporation), but other than the road trip, no public marketing effort had yet been made. A decision was made to formally introduce and kick off the marketing campaign for the Mathatron at the NEREM (National Electronics Research & Engineering Meeting) conference to be held in nearby Boston in early November of 1963. Roy Reach directed a number of product marketing specialists and a technical writer that had been brought in to create polished and professional marketing materials, as well as a professionally prepared user manual. The early production calculators were sold with a user manual written by one of the engineers, and typed up by one of the office staff, then sent out to printer to have copies made. It wasn't pretty, but it did the job until a real user manual could be prepared.

Mathatronics "Model II" Logic Assembly

The NEREM show, along with other electronics trade shows where the Mathatron calculators were shown, were a big hit. By early 1964, orders began coming in at a good clip, and spirits were riding high. Mathatronics had made a name for itself at the high-end of the brand new electronic calculator marketplace, essentially creating it with the Mathatron calculators. No other desktop electronic calculator in the world could even come close to matching the capabilities of the Mathatron.

Unique "bobbin wire-wrap" wiring method (US Patent 3,502,787)

Through 1964 and into 1965, the model 4-24 and 8-48 were good sellers. Mathatronics' engineering expertise went to work improving the capabilities of the 4-24 and 8-48 calculators. In the spring of 1964, a number of new additions were introduced to the calculators as a result of these efforts.

The first improvement was the addition of a ferrite core-based read-only memory (ROM) unit that was added inside the calculator that provided a number of hard-coded programs for advanced math operations such as trigonometric functions (Sine, Cosine, etc.), logarithms, and exponential calculations. This change created the model 4-24 and 8-48 M, S, C and SC sub-models, with advanced math functions addressing Mathematics, Statistical, Civil Engineering, and SCientific types of calculations. The user could then order the specific sub-model based on the types of advanced calculators they had the need for. The specific function to be performed would be selected with the a third rotary switch added to the controls, which would select the appropriate advanced function program in the ROM to be executed, and then the [ENTER] keyboard key would be pressed to cause the ROM program to be executed, carrying out the calculation as if it were being done on the keyboard, but at a much faster pace. The ability to now perform advanced math operations with a twist of knob and press of a button made the Mathatrons even more attractive to potential customers. Along with that, the ability to purchase a calculator with the specific type of advanced math functions required by the customers need was a powerful marketing tool.

Other developments for the calculators involved creating peripheral devices for the machines. The Mathatron calculators had been designed from the very beginning to provide the ability interface the calculator to external peripheral devices, but initially that capability was not utilized. There were two connectors on the calculator, one on the left side, and another on the bottom of the calculator (both covered by block-off plates) provided interface capabilities.

The first peripheral that was developed for the Mathatrons was an input/output interface to allow a Teletype Model 33-ASR to be connected to the calculator. This capability would provide better data printout capabilities than offered by the built-in ticker-tape printer, as well as providing for punched tape data input and output through the Teletype's paper tape reader and punch. This made it possible to allow the calculator to accept machine-prepared input data from the paper tape reader of the Teletype, as well as to punch the results of calculations out on tape, which could then be read into a large computer for further processing. Along with that, the interface allowed formatting of the data sent out to be printed/punched via the Teletype so nice reports could be generated.

Another peripheral that was developed was the Mathatronics APS, an add-on that would provide additional program step and memory register storage. The APS was a pedestal that the Mathatron calculator sat atop, with a connector on the bottom of the calculator plugging into a mating connector on the top of the pedestal, providing a nice platform for the calculator. A control panel to the right of the calculator allowed the operator to control the operation of the APS unit. All of the electronics for the additional magnetic core-based memory was housed in the pedestal.

While the Version I Mathatrons were successful, the rotary switch based controls proved to be a bit tedious in day to day use. A minor redesign of the main logic unit allowed better integration of the advanced math functions. The "Model II Logic Assembly", along with an improved keyboard interface circuit board, provided the logic necessary to allow the rotary switch mode and function selection controls to be replaced by individual keyboard pushbuttons. This design change made the advanced math functions provided in ROM much more accessible to the user, with each function having its own key on the keyboard. With this change, a single key-press would trigger the execution of the ROM program for the desired function. The calculator exhibited here is an example of a Version II Mathatron calculator. The Version II machines were introduced in late 1964.

Ad for Barry Wright/Mathatronics' Mathatron 8-48M Version 2, Circa mid-1966

From an electronics design standpoint, these machines were based entirely on resistor-transistor logic(RTL). This type of logic was rather power hungry, and couldn't run as fast as the diode-transistor logic of machines like the Friden 130, but was the most inexpensive form of logic to use. In such a complicated machine, the savings of using a resistors in place of diodes meant a significant reduction in the overall manufacturing cost of the calculator. While resistors were much less expensive than diodes, there was some tradeoffs made in the design, as pure resistor-transistor logic requires more transistors, which were arguably the most expensive electronic component in the machine. There are over 1000 transistors in the main logic assembly of these machines. This doesn't count the additional transistors in the keyboard circuitry, power supply, and core memory (both RAM and ROM) in the machine. The transistors used in the main logic are primarily PNP Germanium-based alloy-junction 2N404 devices (introduced by RCA in 1957), one of the early transistors which became widely used for digital logic. By the time that these machines were in full production, the 2N404 had been around for quite a long time, and the price per transistor was likely somewhere in the $0.40 range when purchased in quantities. Transistors in the machines seem to come from a variety of manufacturers, including General Electric (GE), Radio Corporation of America (RCA), and General Instrument. From the Mathatronics factory, the tops of the transistors are painted white (potentially to obscure the part number to discourage unauthorized repair), and stamped (or in some cases, hand written) with a number to identify its function in the circuitry. The manufactures of the transistors have been identified from observing machines which have had transistors replaced over the years. Typically, the field-service folks who had to do this tedious component replacement work didn't bother repainting and renumbering the replacement transistor, making the replacement parts easily identifiable.

Initial production of the Mathatron calculators utilized fully discrete component design, primarily resistors and transistors. However, part of the plan for the Mathatron was to use hybrid circuit modules containing multiple resistors in a single inline package, to make the calculators easier to manufacture. These hybrid modules would replace the vast majority of the vertically-mounted resistors in the main logic panels. These hybrid modules had solder pins on the bottom (toward the circuit board) and top. The same wire-bobbin connections were used for connections to the top of the hybrids. Once the outside hybrid circuit manufacturer got its production up to speed, Mathatron production switched over to using the hybrid modules. This change indeed made the production of the calculators faster, reducing the overall production time. However, after a short time, there were problems. The hybrid modules would develop faults, causing the calculators to malfunction. Some of these faults were detected in factory testing before the calculators went out to customers, but, unfortunately, problems started occurring in customer machine shortly after they were put into service. Because of the concerns with the reliability of the hybrid modules, most all calculators that failed in the field, or were returned to a service depot for service would have the failed hybrid module(s) replaced with discrete resistors. The hybrid circuit manufacturer worked to try to figure out why the components were failing, but Mathatronics could not afford to build any more machines that could fail, so production of the hybrid circuit calculators was halted, and the production line re-tooled to return to using discrete resistors. The contract with the hybrid circuit manufacturer was canceled, and all further 4-24 and 8-48 (including various revisions) calculators were built using discrete resistors. Mathatron calculators built with the hybrid modules are very rare today compared to those with discrete resistors. The sad part is that any Mathatron calculators built with the hybrid modules that have survived to this day are virtually irreparable, as replacements for failed hybrid modules are impossible to find.

This exhibit is a work in progress. More information has been gathered, and another Mathatronics 8-48S (Statistical) Version I has been acquired which will soon be added as an exhibit. Please check back from time to time for updates as they become available.

Text and images Copyright ©1997-2023, Rick Bensene.

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