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Wang 370/371 Programmer

At the time of their introduction, the Wang 300-Series calculators were quite ahead of their time. The ability of these machines to carry out advanced math calculations such as logarithms, exponentials, and roots quickly and with reasonable accuracy put the machines in a lofty position ahead all other calculator manufacturers of the time. While Mathatronics had their Mathatron calculators, which could be programmed (either via built-in magnetic-core-based ROM routines, or programs "learned" from the keyboard and stored in internal magetic core read/write memory), these machines were rather slow at performing more advanced math functions compared to the lightning speed of Wang's logarithmic calculating engine. Along with the advanced math capabilities that the 300-series offered, an external punched card reader (the Model CP-1) could be added between the 300-series calculator electroics package, and the keyboard/display unit, to allow rudimentary progrmmability. This gave the machines an even further advantage over competitors. However, the card programming function only provided linear programs...simple sequences of operations with no conditional or branching capabilities. As calculator technology advanced, competitors began introducting calculators that supported more complex programming capabilities. Examples of such machines include the Wyle WS-02 Scientific, Olivetti Programma 101, Monroe EPIC 2000/3000, and the Diehl Combitron calculators. While these machines did not offer the high-speed advanced math functions of the Wang 300-series calculators, they did provide more comprehensive programming capabilities, and while faster than earlier machines, still could not begin to approach the speed of the Wang 300-series calculators for more advanced math functions. And, in a market hungry for less expensive, but more powerful computing power, these machines provided programmability at a lower cost. The programming features of Wang's competitors slowly began to erode Wang's overwhelming market share. The final trigger that led Wang Laboratories to make a serious effort at providing true programmability (with conditional and braching operations) to the 300-series was a surprise invitation that Dr. An Wang (founder of Wang Laboratories) received from executives at Hewlett Packard. Dr. Wang was given a very early preview of Hewlett Packard's upcoming electronic calculator, the HP 9100A. When Dr. Wang saw the computer-like capabilities of the prototype machine, he was immediately struck with the fear that this single machine from Hewlett Packard could potentially unravel the core of his very profitable calculator business. He knew that he had better get something going very quickly to both to bolster the 300-series' capabilities, as well as starting another project to make a calculator that would exceed the capabilities of HP's calculator. If Wang didn't respond propmtly, the precious leadership position that his company had in the lucrative high-end electronic calculator marketplace could be eclipsed the instant the HP calculator came to market.

The Model/Serial Tag on the LOCI Printer

The short-term solution that Wang Laboratories' engineers came up with was the Wang 370 programming keyboard, in conjunction with the Wang 371 punched card reader. This system, introduced in July of 1967, provided a special keyboard/display unit with electronics integrated into it that augmented the programming capabilities of the CP-1 equipped Wang 300-series calculators to include conditional testing, branching, and control of external peripherals. The 371 punched card reader provided the program storage for the system, as the 370 itself had no internal program memory. The 370 executed commands directly from instructions punched into the punched card inserted into the 371 card reader. The 370 could plug into any Wang 300-Series calculator electronics package (though not all 300-Series electronics packages could support the full capabilities of the 370), and provide more advanced programming functions than the standard Wang CP-1 card programmers. The 371 card reader held a single punched card that could hold up to 80 program steps. Up to four 371 card readers can be daisy-chained together to allow programs up to 320 steps to be created, with some limitations in terms of branching between steps contained on cards within differing card readers.

Inside the LOCI Printer

The 370 programming keyboard had its own internal logic that provides the additional functionality. A total of nine Logibloc (Wang's term) circuit boards make up the electronics of the 370. These circuit boards provide all of the logic to interface the keyboard and display with the 300-series electronics package, control the 371 punched card reader, and to decode and execute program steps on punched card in the 371 reader. The Logibloc circuit boards used are of the same form-factor as the Logiblocs used in the 300-series calculators, utilizing the same discrete transistor logic.

The 'MODUPRINT' Printer Module

There are four main components of the 370 programming keyboard. First, the keyboard. The keyboard is of the same design as the other keyboards within the 300-series (e.g., 320K). Discrete microswitches are operated upon by the keystalks to generate signals that are encoded into keycodes, which are then observed by the 370 logic. If the keycode is a function that the 370 performs, it is processed by the local logic within the 370, and if the code is a function to be carried out by the calculator electronics package, it is routed to the electronics package for execution, and upon completion, the 370 can then move on to the next step in the program.

ID Tag on the Printer Module

The next component of the 370 is the display system. The 370 programming keyboard uses the same Nixie tubes and circuit board as the other keyboard/display units in the 300-series, but the method of driving the displays is quite different. Since the display can either show the content of the calculator's W (working) register or program counter and program step information, there is local logic within the 370 that works to allow this display switching to occur. On regular 300-series calculators, the display circuit board contains logic that decodes the numeral and digit select codes and drives the appropriate Nixie tube during its turn to display a number. With the 370, a couple of Logibloc boards perform this function, with the display circuit board containing only the Nixie tubes and decimal point neon indicator tubes.

The next main component of the 370 is the 371 punched card reader(s). These card readers are indentical in mechanical design to the CP-1 card readers that could be used for simple programming of the 300-series calculators. The reader reads the punched card via what is called a "bed-of-nails" method. The punched card is sandwiched between two different surfaces...one surface contains an array of springy contacts, with as many contacts as there are possible punch positions on the card. The other surface contains matching circuit board pads that the springy contacts can connect with if there is a hole punched in the card. The card reader has a latch mechanism that allows the card reader to "clamshell" open, providing the ability for a punched card to be dropped into position, and then the clamshell closed, pressing the springy contacts against the card. A large array of isolation diodes provide for individual selection of 6-bit program codes punched into the cards, with simple transistor circuitry within the 371 providing the decoding of addressing signals from the 370 to select one of 80 program steps that can be punched into the card.

The Logic Card-Cage of the LOCI Printer

Some of the LOCI Printer's Logic Circuit Boards

The Backplane and Power Supply Wiring

The last section of the printer system is the power supply, simple affair made up of two small power transformers, diode recitifers, and filtering capacitors. The voltage supplies do not appeard to be regulated, rather, they are simply set in-situ to deliver the proper voltages, using a tapped wire-wound power resistor.

Operation of the printer is as simple as can be. Simply plug the printer into AC power, plug the cable between the back of the printer and the LOCI-2's "PRINTER" port, and turn on the power to the printer. A single power switch occupies the front panel of the printer, accompanied by a yellow-jewled pilot light to indicate when the power is turned on. The rear panel of the printer contains a fuse holder, the power cord, and a single 50-pin female "Centronics-style" connector to plug in the cable to connect the printer to the LOCI-2 calculator. The calculator has a matching female 50-pin connector on it's back panel that is marked "OUTPUT".

To advance the paper, either it can simply be pulled out manually, or the printer can be commanded to do so from the calculator, by pressing the "CAR'GE RET" key on the Option D-equipped LOCI-2 keyboard (or through a program via operation code 75). To print the content of the LOCI-2's display, the "WRITE" (operation code 11) key is pressed. The printer can print about 1 line per second, give or take a little.


Thanks to Sarah Hafner for the opportunity to acquire this wonderful artifact.
Thanks to Charles Levinski for the information on modular printer technology
Text and images Copyright ©1997-2021, Rick Bensene.