Peripheral-Sharing Unit Aims To Unravel Output Snarls

One afternoon the vice president of our toxicology department called me into his office to take a look at some mysterious printing problems he was having with the department’s computer. Documents suddenly stopped printing in mid-sentence, or vanished entirely between computer and printer. And often when this happened, the entire computer system had to be shut down and started before printing could resume. The problem wasn’t hard to find. The department’s system consisted of a number of line switching devices, a 512K buffer, and a lot of cables. All of this equipment was in place to allow three personal computers to share three printers (a Hewlett-Packard Laser Jet, an IBM Quietwriter, and a dot matrix printer). Whenever someone wanted to change the print destination, they had to get up from the terminal they were using, set the appropriate switches, send a test print, and cross their fingers. Not only was the system inefficient, it was a functional nightmare. Sometimes the switches were set wrong or cables were jiggled out of place. It was clear that my colleagues needed help, and it sounded like a job for the Logical Connection. The Logical Connection is a peripheral-sharing device made by Fifth Generation Systems, Inc. of Baton Rouge, La., and it fit the needs of the toxicology department perfectly. It has switching capabilities, a buffer, and ports for cables built into a compact unit (14 inches wide, 5 inches deep, and only 1 inch tall). Up to 45 printers, computers, and modems can be connected in a variety of ways by daisychaining them with simple twisted-pair cable connected to port 0, a high- speed, RS-485 serial port. My favorite feature of Logical Connection is that it makes it possible to choose the print destina- tion from a memory resident menu that can be called up with a single keystroke, so I don’t have to leave my PC to print a document. The device is also easy to install and use: The manual’s “Quick Start” instructions for setup and hookup are straightforward, making it simple for even a novice to set up. The system is equipped with two parallel input ports, two parallel output ports, and four serial ports, all of which use DB-25 pin connectors. This way, existing printer cables can be used to connect from the Logical Connection to the peripherals. The computers connect to the switching device using 25-pin female-to-female cables for serial ports and male-to-female cables for parallel port connections. The Logical Connection can be purchased with an internal 256K ($495) or 512K ($595) buffer. These buffers allow scientists sharing a single printing device to submit jobs simultaneously. The first job to arrive is the first to be printed. Much of the Logical Connection’s versatility and ease of use comes from the two software prograins (LCSETUP and POPLC) that are included with the package. When LCSETUP is run, the computer screen shows a miniature diagram of the Logical Connection along with any devices that are connected to its ports. Extra peripherals can be easily added to or deleted from the unit box with a series of keystrokes. In addition, the LCSETUP program comes with ten preset configurations that cover most equipment situations. All the scientist needs to do is find the diagram that most closely matches the setup of peripherals in his or her lab and change the labels. For example, the scientist can change the “computer #3” that appears on the LCSETUP screen, to “Ted’s computer” or change “dot matrix printer” to “Sherrie’s printer,” making it easier for each person in the lab to know which peripheral he or she is accessing. For serial port connections, LCSETUP allows the scientist to set the baud rate, parity, word length, handshaking protocol, and other communication parameters that allow the computers and printers in the lab to talk to each other. The serial ports can be set at “bidirectional” to communicate with a bulletin board via a modem and download any desired files. LCSETUP also lets the scientist define four special printer codes, or “control codes,” that can be used to reset any of the peripherals. For example, it would be possible for a scientist to send a form feed to a laser printer or change the print size from 10 to 17 characters per inch, by choosing the commands at his or her PC keyboard. The other software program, POPLC, is a memory resident program that controls switching between peripherals. A window is called up to the screen showing a list of the peripheral devices as well as the printer codes. The scientist simply chooses the print destination on the menu, hits return, and the device is ready to use. The start-up command for POPLC can be added to the Autoexec file so that it is automatically loaded every time the computer is turned on. We installed the Logical Connection in our toxicology department, and now all the printing problems have magically disappeared. People in other areas have noticed its advantages, as well. The Logical Connection has now been installed in a chemistry lab where a researcher wanted to tie together two IBM PC computers and two dot matrix printers that are in different parts of the lab. Also, our pathology staff has had the Logical Connection installed in two separate secretarial staff areas. They each wanted the freedom and flexibility of having two personal computers access both an IBM Quietwriter and a Hewlett-Packard Laserjet. The Logical Connection is a versatile product that has almost unlimited applications in the laboratory or any other environment. The only thing I can think of to complain about is that even the 512K internal buffer is limiting—it is quickly used up if many PCs are hooked to a single printer. However, when compared to investing in a network or buying a laser printer for every personal computer, Logical Connection’s benefits are unprecedented. Steven Yuhas is a computer specialist in the toxicology department at Warner-Lambert/Parke-Davis Research, Ann Arbor, Mich.

Peripheral-Sharing Unit Aims To Unravel Output Snarls

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