Wang Model 360SE Calculator System

by Rick Bensene

History


Here's another wonderful piece of calculating history. This is a Wang Model 360SE Calculating System. Its not just a calculator, it's a system of calculators.

Wang Laboratories, founded by Dr. An Wang as a one-man electronics company in 1951, became famous for revolutionizing electronic calculators by providing higher level math functions which previously were only available on very expensive computer systems. Dr. Wang invented a combination of digital electronic circuits which used a method called 'factor combining' to generate the base e logarithm of any number. (This circuit was patented in 1968). The properties of logarithms make it much easier to perform functions such as square root, raising numbers to powers, and dramatically simplifies multiplication and division via electronic circuits. Using any other method to perform such calculations would have taken far too many components, resulting in a larger and more expensive machine.

The 300-series of calculators were the second line of electronic calculators introduced by Wang. The LOCI (an acronym for LOgarithmic Computing Instrument) machines, which were rather clunky and large machines, were the first electronic calculators sold by Wang, introduced in January of 1965. The LOCI machine sold originally for $6500, but could perform complex calculations with single keystrokes (as compared to the complexities of making mechanical calculators do the same calculation), in a fraction of the time of older mechanical calculators, and were significantly easier to use. The LOCI calculator embodied Dr. Wang's logarithmic calculation circuit, and proved to an eager marketplace that the electronic calculator had a place in engineering and scientific calculations. The LOCI machines today are extremely rare and are generally considered museum pieces.

The 300-series machines went into mass production in late 1966, with my particular machine apparently being produced in mid-to-late 1967, based on date stamps on the boards.

A 300-series system in general consisted of a central electronics package, and keyboard/display unit(s), which plugged into the central electronics package. The keyboard/display units provide the operator interface to the machine.

The electronics package consists of a number of standard-sized printed-circuit cards, which plug into edge-card connectors, which are interconnected via a hand-wired point-to-point backplane. The circuit cards have components and traces on once side, and traces only on the other side, with jumper wires providing connections between sides of the board. In all of the general circuitry of the machine, standardized components are used. Most of the transistors are of the same type, with exceptions in areas such as the timing and control circuitry, core stack drivers and amplifiers, and display driving circuits. The logic appears to be fairly generic diode-resistor/transistor logic for gating functions, and basic types of flip-flop circuits for registers, counters, and latches.
Core memory is used for all of the working registers, with a single PC card which has 4 small core arrays situated on it, along with gating diodes. Another two or three boards have the timing, driver, and amplifier circuitry to run the core array.

There were two versions of the 300-series electronics packages; the E model, and the SE model. The E-version of the machines provided one connector for plugging in a keyboard, and though you could, using special connectors, connect multiple keyboard/display units on these machines, only one keyboard/display unit could be used at a time. The SE-version machines provided four connectors for plugging in keyboard/display units, and all four keyboard/display units could operate at once as 'independent' calculators.

There were four models available for each type of electronics package. It isn't clear (and I'd appreciate hearing if anyone knows for sure) if there were any differences at all in the electronics packages between the different models within a series (E or SE). It appears that the electronics package could have been the same between the 'low-end' 300E and the 'high-end' 360E, with the difference being the capabilities of the keyboard/display unit that came 'standard' with the machine. I'm not positive of this, though.

The Model 300E system which was the 'base' model, came with the 300K keyboard/display unit, which provided access only to add, subtract, multiply, and divide functions
The electronics package consists of a number of standard-sized printed-circuit cards, which plug into edge-card connectors, which are interconnected via a hand-wired point-to-point backplane. The circuit cards have components and traces on once side, and traces only on the other side, with jumper wires providing connections between sides of the board. In all of the general circuitry of the machine, standardized components are used. Most of the transistors are of the same type, with exceptions in areas such as the timing and control circuitry, core stack drivers and amplifiers, and display driving circuits. The logic appears to be fairly generic diode-resistor/transistor logic for gating functions, and basic types of flip-flop circuits for registers, counters, and latches. Core memory is used for all of the working registers, with a single PC card which has 4 small core arrays situated on it, along with gating diodes. Another two or three boards have the timing, driver, and amplifier circuitry to run the core array.

There were two versions of the 300-series electronics packages; the E model, and the SE model. The E-version of the machines provided one connector for plugging in a keyboard, and though you could, using special connectors, connect multiple keyboard/display units on these machines, only one keyboard/display unit could be used at a time. The SE-version machines provided four connectors for plugging in keyboard/display units, and all four keyboard/display units could operate at once as 'independent' calculators.

There were four models available for each type of electronics package. It isn't clear (and I'd appreciate hearing if anyone knows for sure) if there were any differences at all in the electronics packages between the different models within a series (E or SE). It appears that the electronics package could have been the same between the 'low-end' 300E and the 'high-end' 360E, with the difference being the capabilities of the keyboard/display unit that came 'standard' with the machine. I'm not positive of this, though.
The 300K Keyboard LayoutThe 310K Keyboard LayoutThe Model 300E system which was the 'base' model, came with the 300K keyboard/display unit, which provided access only to add, subtract, multiply, and divide functions. The Model 310E system provided the model 310K keyboard/display unit, which added access to squaring and square root functions.
The 320K Keyboard LayoutThe 360K Keyboard LayoutThe Model 320E system added to the 310's functions with addition of e^X and Loge. The Model 360E system came with the 360K keyboard/display unit, which added access to four store/recall memory registers in addition to the functions provided by the 320K keyboard/display unit.
There was a separate "SE" system available in each of the 300-series models. The "S" stood for 'Simultaneous'. The SE model electronics packages were equipped with connectors for four keyboard/display units, and they all operated as independent, simultaneous calculators.

In the "SE" model machines, the electronics package 'timeshares' between each of the keyboard/display units, on a round-robin basis, with each 'slice' of time ending when an operation is completed, I.E.: if one keyboard/display unit is performing a calculation, the others are locked out until that operation completes, then the other units are given their slice of time. Generally, this time-slicing is performed quickly enough that it appears to each user as if they have their own dedicated calculator.

The SE-series machines followed the same model-numbering scheme as the E-series machines, with the 300SE, 310SE, 320SE, and 360SE models being offered. This keyboard/display unit is the 'trig' unit, with a sequencing unit built into the keyboard unit that provides a ROM-based 'program' for calculating Sin, Cos, ArcSin, and ArcTan functions. The keys for these functions are at the upper-left of the keyboard.
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Trig function sequencer boardThis picture shows the sequencing board inside the 'trig' keyboard, which provides 'virtual keypresses' to the electronics package to perform trig functions. There's a small slide switch on the right center of the board that is marked "Cont/Step".

Diode-ROM arrays containing Trig function programs Immediately to its right is a switch which, when pressed, will perform one 'program' step of a trig operation when the slide switch is in the 'Step' position. Diode-ROM arrays on two plug-in cards are mounted on the back of the sequencer board which contain the 'programs' for the trigonometric functions.

The 300-series machines calculate to a full 14 digits of accuracy, but only display 10 digits. This makes the machine very accurate. Since the Wang calculators used logarithms to perform multiplication and division, and even though Dr. Wang's log-generating circuit produced very accurate results, many are logs are transcendental numbers which can never be represented with 100% accuracy no matter how many digits you calculate them to. Therefore, the LOCI machines, when doing multiplies and divides, could come up with results which would be slightly off. An example would be multiplying 6 by 8. The LOCI could give an answer of 47.9999999. To make the 300-series more intuitive, these machines got the benefit of a special circuit that provided a 'round off' function, which would cause such 6 x 8 to yield 48.0000000, which made the 300-series machine much more useful to 'non-technical' (I.E.: business and financial) users.
An individual Wang Nixie TubeThe display on the 300-series machines is via Wang-manufactured "Nixie" tubes. Nixie tubes display numbers by having ten different stacked electrodes which are formed into the shape of digits, all packed into a little glass envelope which looks like a small vacuum tube, filled with neon gas. When a given electrode is energized, the neon lights up around the electrode, forming a glowing orange number. Nixie tubes were commonly used in electronic equipment requiring numeric output through the early '70's, when other less complex (and expensive) display technologies displaced them. An 11th special Nixie tube, situated to the far left of the display, contained only a + and a -, is used to indicate the sign of the result. Decimal points are indicated by small discrete neon bulbs which are situated between the Nixie tubes. The machine does full-floating point math, which was rare for early electronic calculators. Overflows result in the overflow digits being discarded, and an 'overflow' neon bulb at the far left of the display that blinks when a detected overflow condition occurs.
The electronics package provides two add/subtract accumulators (called the 'left' and 'right' accumulators, based on their keys location relative to the numeric keypad on the keyboard), 4 memory store/recall registers, multiply, divide, square root, X^2, Loge(X), and e^X functions for each keyboard/display unit. It's up to the keyboard/display unit to provide access to these functions.

The machine used a unique method of entry for problems. Add and subtract operations were done in postfix form, I.E.:

10 + 12 - 6 would be entered as: 10 + 12 + 6 -

Multiplication and division used an 'ENTER' key, I.E.:

10 X 12 / 16 would be entered as: 10 ENTER 12 X 16 /

Multiplication and division were performed using addition/subtraction of logarithms. Entering a number, followed by the "ENTER" key would cause the Loge of that number to be extracted and placed in a hidden register (not a stack, as in RPN style calculators). Entering the next number, followed by either the multiply or divide key, would cause the loge of the entered number to be extracted, then the result added (in the case of multiply) or subtracted (in the case of divide) to/from the hidden register, then the antiloge of the result extracted, and put into the display register.

Source: Rick Bensene's Old Calculators
French translation made by Mary Orban .

Copyright Rick Bensene - Revised: March 21, 2015.
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