The Wang 360E is an example of Wang Laboratories' 300-Series calculators targeted at the single-user market. All of Wang's 300-series calculators used a modular approach, with an electronic package that connects to remote keyboard/display unit(s) via a cable and plug-in connection. The benefit of this method was that the keyboard/display unit was quite small (listed in advertising as "about the size of a desk telephone"), consuming a lot less desk space than the monolithic "desktop" calculators of the time, such as the Sharp Compet 20 or the Monroe 770. The electronic package, which could be located up to 200 feet from the keyboard unit, contained all of the calculating brains and the power supply for the calculating system, and the keyboard/display unit simply contained the circuitry to drive the display and encode key-presses from the keyboard.

The Wang 300-series was an outgrowth of Wang's first generation electronic calculator, the Wang LOCI-2. The LOCI-2 was a bit cumbersome for non-scientific users to operate, so Wang developed the 300-series calculator to address a wider marketplace. The main selling point of Wang's early electronic calculators was their ability to perform scientific functions such as logarithms and roots, with single-key ease. Other calculators of the era could, at best, perform a square root operation, but none could do logarithms, which are a mainstay of scientific and engineering calculations. The only other calculators of the time that could perform these more complex math operations were those that were programmable, such as the Olivetti Programma 101, or the Mathatronics Mathatron calculators. However, on these machines the calculations would have to be performed by writing complex programs, which required expertise to create. Plus, the programs typically would take significant time to execute -- a natural logarithm program may take 5 to 10 seconds to generate a result using a program on one of these programmable machines, whereas the same operation using Wang's built-in logarithm capability would take a few hundred milliseconds. In the course of complex engineering or scientific calculations, the time savings afforded by Wang's logarithmic calculating capability could be very significant.

Silk-screened Label Identifying the Electronic Package

The 300-series calculators were developed beginning in late 1964, and prototypes were shown at various trade shows and conferences in the late part of 1965. Production of the 300-series calculators began in earnest in early 1966. The early 300-series calculators were all single-user units, with one keyboard/display unit connected to the electronic package. There were special devices called "T Connectors" that would allow two keyboard/display units to be connected to one electronics package, but when these were used, only one of the connected keyboard/display units could be in use at any given time. When one keyboard/display unit was turned on, the other was locked out until the one that was in use is turned off, then the other keyboard/display units would be available for use. There was a special "T" that provided a one port for plugging in a priority keyboard/display unit that if turned on would immediately turn off the other unit connected to the "T" This "T" capability allowed one electronics package to be shared amongst a number of keyboard/display units, but with only one keyboard/display unit active at any time.

An example of the Wang 300-Series "T" connector

In early 1967, Wang introduced multi-user timeshared (Wang called them "Simultaneous") versions of the 300-series calculator electronics package (such as the Wang 360SE) that would allow up to four users to simultaneously share a single electronics package. The same T-Connectors could be used with these simultaneous units, but again, only one calculator on each of the four channels of the simultaneous electronics package could be used at any given time when using the T Connectors. Wang Laboratories offered kits that could be used to provide wall plates and wiring that could be pre-wired into office spaces so that there would be an outlet to plug in a keyboard/display unit in each office space, and through the use of T connectors placed in the network of wiring, a cooperative sharing of a simultaneous calculator electronics package could be made such that a fairly large number of keyboard/display units could be connected up to a "network" of T'd connections through the wall plates, with up to four stations active at any given time. This would allow the cost of the calculator system to be spread across as many stations as were on the "network", definitely saving money versus having to provide a conventional desktop calculator in each office, or providing shared desktop calculators in a common space that users could share.

Because the 300-series calculators utilized Wang's unique logarithm-generating circuitry, they were able to perform much more complex calculations in a fraction of the time of other calculators of the day. For this reason, the Wang 300-series calculators started selling like hotcakes into both scientific and engineering customer bases, propelling Wang Labs on a meteoric rise to the top of the electronic calculator business.

The calculator system exhibited here is an example of the success of Wang's 300-series. The 300-series calculators were designed during a time when integrated circuits, which we all take for granted today, were not a practical reality. Discrete transistors, combined with myriad diodes, resistors, and capacitors, make up the circuitry of all of the 300-series calculators. Even though by late 1970, when this particular calculator was manufactured, it was still possible for Wang to market the 300-series calculators against those of competitors, though prime time for the sales of the 300-series calculators was quickly nearing its end. By the time this particular calculator was made, small-scale integrated circuits had pretty much taken over for electronic calculator circuitry, and large-scale IC's were on the horizon, making shirt-pocket versions of scientific electronic calculators a soon-to-be reality. Even though the technology was changing rapidly, Wang had so captured the market with the 300-series calculators that they could get away with selling their "old" all-transistor machines long after the technology was considered to be outdated, sheerly on the inertia of the popularity of the machines.

Final Quality Assurance Sticker

The 360E exhibited here is a little bit confusing in terms of its history. All of the internal date stamps and codes indicate that this machine was manufactured in the late 1970 time frame. The final QA(Quality Assurance) sticker located inside the machine on the backplane circuit board (see above) shows a date of December 28, 1970. However, the pre-ship QA sticker on the outside of the machine indicates a date of February 28, 1972! Wang Labs cranked these machines out in prodigious volume in the late 1960's and early '70's in order to meet customer demand. It could be that, as competition in the calculator marketplace heated up in the early 1970's, there may have been a buildup of inventory that resulted in completed calculators sitting in inventory for as long as 12 to 18 months before being sold and receiving their final pre-shipment quality assurance checks.

Model/Serial Tag and Pre-Ship QA Sticker

There were five different versions of "E" (single-user) electronic packages that were sold. The Model 300E and 310E electronics packages were the low-end of the scale, forsaking access to the single-key scientific functions and memory registers. The Model 320E electronics package provides full access to the single-key scientific functions, but no memory register capability. The 360E, and the later 362E electronic packages provided memory capabilities in the form of store/recall registers, with the 360E providing four registers, and the 362E providing twelve, with the ability to split some memory registers in half, creating two memory registers that had the capacity of five digits.

All of the E-type (single-user) electronic packages supplied the same basic arithmetic functionality, with two general-purpose accumulators. Wang's amazing logarithm generator was embodied in another register that serves to accumulate logarithms. Multiplication and division, and the scientific functions of electronics packages are performed using the logarithm accumulator register, though its existence is generally hidden from the user.

A diversion into the concept of logarithms is in order here. A logarithm, simply stated, is the power portion of the representation of a number in a particular base. For example, the base ten logarithm of 1000 is 3, because 10 to the third power is 1000. Likewise, the base ten logarithm of 125 is 2.09691 (accurate to five decimal places), because 10 to the 2.09691 power is roughly 125. Logarithms were the basis by which the slide rule operated, allowing a simple device calibrated with logarithmic scales to perform multiplication and division.

The Wang 300-series calculators don't use base ten logarithms in their logarithm generating circuitry. Rather, they use base e logarithms. e is a number (roughly 2.7182818, though it is a transcendental number, and is thus never able to be stated exactly) with special mathematical significance. Using any base logarithms, it is possible to perform multiplication and division by simply adding (in the case of multiplication) or subtracting (in the case of division), the logarithms of the numbers to be multiplied or divided, then taking the anti-logarithm of the result. For example, to multiply 3 by 5, the base e logarithm of 3 is calculated (which is 1.098612, accurate to six digits behind the decimal point), and the logarithm of 5 is calculated (1.609437), and the two logarithms added (totalling 2.708050). The anti-log of this result is then calculated, resulting in 14.999714, a result that, while not completely accurate, is close, considering that the logarithms in this example are only stated to 6 digits behind the decimal point. The 300-series calculators figure logarithms accurate to 12 digits behind the decimal point, and incorporate special rounding logic, so that multiplying 3 by 5 correctly results in 15.00000000 rather than 14.99999998.

Along with multiplying and dividing, the logarithm generator can be used directly for performing logarithms, exponentials, square roots, and squaring with the single press of a key.

Closer View of the Wang 360K Keyboard/Display Unit

The mathematical capabilities of the electronic package are accessed by attaching a keyboard/display unit, of which a wide range were available. See the exhibit on the Wang 360SE for much more detail on the 300-series keyboard/display units. In short, the available keyboards were: 300K, 310K, 320K, 320KT, 320KR, 360K/362K, 360KT, and 360KR. The KR/KT keyboard/display units added additional circuitry inside unit in the form of a sequencer and a read-only memory (ROM) made from hundreds of individual diodes that effectively encode a series of key presses to calculate the trigonometric functions with one key press.

Wang 320K Keyboard with Wang CP-1 Card Reader

All of the above 300-series keyboard/display units could be made programmable (in a limited fashion) with the addition of the Model CP-1 punched card reader to allow keyboard steps to be automated. The CP-1 enabled sequences of key presses to be coded onto punched cards in an octal (base 8) code, allowing the key press sequences to be played back as if they were being entered from the keyboard. This method allowed simple programs to be created. The CP-1 card programmer only provided linear programs with no automatic looping or branching capabilities.

Wang Model 370 and 380 Programming Keyboards

Later introductions to the 300-series calculators included two truly programmable keyboard/display units, the Model 370 and Model 380. The Model 370 keyboard/display unit used attached punched card reader(s); the Model 371 Master and 371 Slave readers for providing the program. Up to four card readers could be connected to the 370, allowing programs up to 320 steps in length. The 370 programmer furnished the ability to code conditional testing and branch instructions to allow much more complex programs than could be performed using the CP-1 card reader and standard 300-series keyboard/display units.

The Model 380 recorded program steps entered on the keyboard onto a removable magnetic tape cartridge that was inserted in the back of the keyboard/display unit. Once program steps were recorded on the tape, they were able to be executed as a program. Like the punch-card programmable 370, the 380 provided decision-making and branching instructions. Both the 370 and 380 keyboards added more computer-like programming functions to the 300-series calculators that allowed the (by that time aging) 300-series calculators to compete with programmable calculators from other manufacturers such as Wyle Laboratories, Hewlett Packard, Casio and others. By the late 1960's, it was clear that Wang's 300-series calculators were becoming dated, and Wang began development of the Wang 700-series calculators to respond to the much more powerful calculators being introduced by its competitors.

The Backplane of the 360E Electronic Package

The 360E electronic package is significantly less complicated than the multi-user "SE" electronics packages. A total of 22 circuit boards (versus 32 in the four-user 360SE) make up the logic of the machine. The circuit boards plug into a printed-circuit backplane, in contrast to the 360SE, which uses a hand-wired backplane. There are a total of five common circuit boards between the 360E and the 360SE, with the rest of the boards being unique between the two machines.

One of the Logarithm ROM Circuit Boards from the Wang 360E

A total of 491 transistors are used in the logic of the 360E electronic package. Information from ordinal Wang Laboratories documentation indications that the 360E electronic package was essentially a retrofit of the 320E electronic package, adding the additional circuitry to provide the four store/recall memory registers. A look at the backplane of the 360E shows a curious modification involving an additional backplane circuit board piggybacked on the main backplane as well as a number of hand-wired connections that are likely related to the store/recall memory register functionality.

The 360E Core Memory Board

Regardless of whether the electronics package provide access to store/recall memory registers, all of the 300-series electronics packages use magnetic core memory for storage of the calculator's arithmetic working registers. The 360E and 362E electronics packages also use the core memory subsystem for storage of the store/recall memory registers. This multi-function use of the core memory subsystem reduces the complexity and component count of the machine significantly versus the use of transistorized flip-flop registers, used in Wang Labs' earlier Wang LOCI-2.

A Closeup View of the Core Memory Array

The core memory system consists of a single board that holds the magnetic core array, current steering diodes, and the memory sense amplifiers and inhibit drivers that interface the magnetic core to the rest of the electronics of the calculator. Also included on the core array board is a constant-current power source that provides a specific and stable current level that is calibrated to be 1/2 of the current required to flip the state of one magnetic core. By providing this current to one of the wires in the vertical direction, and another wire in the horizontal direction that intersects in a single core, the full current necessary to flip the state of the core exits. All of the other cores in the row and column will only see half of the current necessary, and thus will remain in their current state. The core memory addressing circuitry that selects the rows and columns for a given memory address is contained on other circuit boards. The core array in the 360E is arranged as four planes of 16 by 8 bits each, for a total of 512 bits. This organization allows for storage of eight 64-bit numbers addressed four bits at a time. Each register in the calculator consists of 64 bits, represented by sixteen 4-bit chunks. Decimal digits are represented internally as Binary-Coded Decimal (BCD). One digit is used to represent the sign of the number. Another digit represents the position of the decimal point within the number, and fourteen digits represent the number itself. Ten of the fourteen digits are displayed, with the remaining four digits used as guard digits to increase the accuracy of the machine. Four of the eight registers are used for the store/recall memory registers, and the remaining four registers make up the working registers of the calculator's logic, including the "W" (Working) register, from which the display is generated, and into which numbers from the keyboard are entered, the two accumulator registers, and the "L" (Logarithm) accumulator register.

Inside the 360E Electronic Package

Besides the circuit boards and backplane of the calculator, the electronic package also contains the power supply for the system. The power supply is a fairly basic linear power supply, with a surprisingly small transformer, the usual assortment of large computer-grade filter capacitors, rectifier diodes, and transistorized voltage regulation circuitry.

An original Wang Service Report and Invoice for Repairs to a Wang 360E in 1971
Click Image for Larger View
Document Courtesy Gene McGough

The power supply provides voltages to the backplane for distribution to the circuit boards, as well as to the remote keyboard connector, providing power to the keyboard/display unit. It appears that somewhere along the line, Wang added circuit breakers to the main logic supplies. Two externally re-settable circuit breakers are installed such that it is clear that they were an afterthought, not included in the original design of the electronic package. I have seen earlier versions of the 300-series E-type electronics packages that do not have these circuit breakers.

Krause was fascinated with electronic storage and calculating systems, and over time developed a number of custom inventory control and mailing list management systems for a variety of customers. Krause had seen Wang Laboratories' 300-Series calculators at a trade show in early 1966, and immediately realized that Wang's 300-series calculators could serve as the numerical processing brains of a general purpose computer. Arrangements were made for K & M Electronics to become an OEM (Original Equipment Manufacturer) customer of Wang Laboratories, purchasing the Wang 360E electronics package (without keyboard/display unit) at a quantity discount for integration into a computer system. The result was a $15,000 business computer called the KM 220, introduced in May of 1968. The KM 220 integrated the 360E electronics, a Model 35 Teletype, a high speed paper-tape reader/punch, and a program/data storage system based on X-Y accessible random-access 6-inch wide magnetic tape loop. A data communications interface rounded out the system, allowing for the KM 220 to be connected to other KM 220's, or, to large mainframe systems for further processing of information generated by the KM 220. The result was a general purpose, programmable computer system that could be programmed for any number of business applications including inventory, payroll, invoicing, general ledger, and just about any other small to medium scale business application. Along with business functionality, the KM 220 could also perform scientific calculations due to the Wang calculating engine embedded within, which provided fast square root, logarithm and antilogarithim functions. A scientific applications that was developed for the KM 220 was data reduction processing of weather raw weather observations, with the result fed to large computers for generating weather forecasts. If anyone out there has any information on the K & M Electronics KM 220, or better yet, may have a lead on the existence of same, please Contact the Old Calculator Museum right away.

The Wang 4000 computer system and the K & M Electronics KM 220 are just a few examples of the amazing adaptability of the Wang 300-series calculator design. The fact that these computer systems could be built based on electronics designed to serve as a calculator is a testimony to the ingenuity and foresight of Wang Laboratories' engineering talent.

One aspect of the Wang 300-series calculators that is typically not in the forefront from a historical standpoint was Wang Laboratories' world-class customer support for the calculators. A major part of the success of Wang Laboratories in the calculator business, despite initially being an unknown newcomer to the market, was the service and support of its products. Dr. Wang was insistent that the calculators that Wang Labs sold to customers would first be of the highest quality possible at a reasonable price, and that the calculators would always work straight out of the box. With electronic calculators being complex electronic devices, this was no small feat, but the Quality Assurance department that Dr. Wang created to support his calculators was staffed by engineers and technicians that knew the devices inside-and-out, and were tasked with making sure that every calculator was in perfect operational and cosmetic condition before it was boxed up for shipment to a customer. Dr. Wang also made sure that his company stood behind the calculators it sold by providing a warranty of a full year, where other electronic calculator companies at the time were offering warranties of 90 to 120 days. Wang Labs had build out a nation-wide network of its own service centers, as well as allowing independent contractors to service the calculators once the contractor had completed a thorough training program as well as allowing Wang Labs to assure that their level of support was just as good as Wang's own support staff.

Wang Labs offered customers the option to purchase extended maintenance contracts that were reasonably-priced, and meticulously executed on a scheduled basis by Wang's field service technicians. With a service contract, a field technician would make regular visits to the customer's location and would first perform a full set of diagnostics on the customer's calculator. If any faults were found in the process of executing the diagnostics, they were immediately repaired free of charge. Once the machine passed the diagnostics, it would be thoroughly cleaned inside and out, removing the usual accumulation of dust and bits of office detritus that inevitably end up inside the machines...things like staples and paper clips that can have devastating effect if they happen to short out circuitry. The keyboards were cleaned and aligned so that the keys all had positive and consistent operation, and if there was any sign of wear in the keyboard assembly, it would either be repaired, or the entire keyboard assembly replaced if repair was not practical. Any Nixie tubes that were dim or not lighting fully would be replaced with new tubes, and fresh fuses were always installed regardless of the state of the existing fuses.

Dr. Wang insisted that any repairs that needed to be made during the warranty period of a calculator were performed promptly and properly every time, with information gathered on field failures processed and turned into production process improvements to eliminate sources of common failures. Dr. Wang was very clear that his customer support representatives must be at the very "best in class" in providing the best support experience for the customer as was humanly possible. If a customer's calculator was malfunctioning, it was absolutely a top priority to get the machine back up and running perfectly for the customer as quickly and efficiently as possible. In many cases, Wang field-service technicians would go above and beyond the call of duty to assure that their customers got the red-carpet treatment no matter the situation.

One of the tools that made this possible was that Wang service technicians were provided with a kit of spare parts that would allow them, with assistance from detailed troubleshooting instructions and thorough familiarity with the operation of the calculators, to replace circuit boards from the tested and burned-in boards in the technician's service kit. Replacing failed modules rather than trying to diagnose problems down to the component level made getting the customer's calculator back in tip-top shape a much quicker and easier process.

Since there were quite a number of different circuit boards required across the line of 300-series calculators, as well as needing room for larger parts such as spare Nixie display circuit boards, the spares kit consisted of two oversized, heavy-duty briefcases with sturdy wooden frames, brass hinges and latches (lockable), and a hefty leather carrying handle. Inside the base of the case, there were sheet metal dividers with wooden guides pop-riveted to the dividers that would made convenient edge guides for the spare Wang LogiBloc circuit boards. In between the two columns of circuit cards were spaces for larger items such as spare display circuit boards, keyboard circuit boards, parts for the CP-2 punched card readers, and various smaller parts like fuses, Nixie tubes, cables, and other miscellaneous items. The upper part of the case had typical briefcase dividers for storing paperwork, which in the case of the service kits, had pads of service writeup forms, self-adhesive service tags for placing inside the covers of repaired devices to log what work had been done to the customer's machine, as well as service contract identification tags.

Wang Laboratories 300-Series Spare Parts Kit Bottom Section, Briefcase #1

The first case contains mainly spare circuit boards, with a space in between the two columns of circuit boards for storing spare display circuit boards and other smaller components such as spare cable assemblies used to connect a keyboard/display unit to the electronics package.

300-Series Spare Parts Kit Bottom Section, Briefcase #2

The second briefcase has one column of spare circuit boards, as well as a small second column for a few more boards, with the remainder of the column reserved for storage of larger parts, such as spare keyboard circuit boards (populated with micro-switches and toggle switches as well as discrete components), and circuit boards for the CP-2 Punched Card Reader. The center section between the two columns was available for storage of smaller items as it is in the first briefcase. The larger spare parts in the right-most section of the second briefcase, and the smaller parts in the center sections of both briefcases were wrapped in a layer of soft protective foam to prevent damage as the briefcases were hauled around. Between the two briefcases the complete inventory of all of the logic circuit boards necessary to replace every type of circuit board in every model of Wang 300-series calculator, with exception of the Model 362E electronics package which was not yet announced when this particular parts kit was produced.