Classic Computer Magazine Archive COMPUTE! ISSUE 19 / DECEMBER 1981 / PAGE 45

S Y Z Y G Y RS-232 Condition Testers

Sanford I. Gossman
San Rafael, CA

S Y Z Y G Y (pronounced "siz-a-gee") is a small, and relatively new, company in Covina California (256 West San Bernardino Road; 91723). They produce a line of RS-232 testing devices which includes two LED devices that monitor the condition of the connections that interface RS-232 devices, or ports. The quality of their products demonstrates what can be done when a manufacturer limits himself to one type of product and does a job right.

S Y Z Y G Y makes two RS-232 line-condition testers. Each are "pocket size," measuring approximately 3×2×½ inches. Each has a male RS-232 connector on one end, and a female connector on the other. Each has eight LED's wired so as to monitor the seven most commonly used signals (pins 2, 3, 4, 5, 6, 8, & 20: TD, RD, RTS, CTS, DSR, DCD, DTR). The eighth LED, labeled "TEST," can be jumpered to any pin not having a light wired to it, so that its status can be monitored.

No Batteries Needed

The devices are powered by the RS-232 signals, so no batteries are required. Current-limiting circuitry assures a constant current over the voltage range permitted by the RS-232 standard, and provides a simple "go, no-go" indication.

The least expensive of the two products is called the "Test Set" and sells for $89. Each of the 25 pins are wired through, and a single 26-pin header provides a means to connect one pin to another.

The "top-of-the-line" model is designated the RS-232 Patch Set. It sells for $111. It is the model I have been using for the past two months.

The difference between the two is that the Patch Set has none of the connectors feeding through. Instead, there is a 26-pin header on each end. The unit comes with a generous supply of single and double jumpers. The wires are used to connect the pins manually: either to their corresponding number, or to another pin, or pins, for testing. The advantage of this scheme is that it permits you to easily break the connection of a pin, by merely pulling a jumper. In this way, you can determine what signal is present from each device separately.

Easy Status Checks

I am in the process of writing a series of reviews of RS-232 modems. Most of the equipment represents a new product, and there is no software provided that will permit operation in my equipment environment. So, I have been busy writing software.

The Patch Kit has proven invaluable. With the documentation from some manufacturers being sketchy, at best, it has been imperative for me to know the status of each of several key connections. With the Patch Kit it was easy. Without it I would have been switching a logic probe between pins almost endlessly.

The ability to segregate signals helped me greatly when I was having difficulty reading a status signal from a modem, through software. Theory said that what I was doing was correct, but I was both baffled and frustrated. Because I was able to determine the status of the problem signal line at "each end" of the connecting cable, the source of the problem was discovered easily.

By disconnecting the corresponding jumper and "reading" the signal as it appeared (both coming from the modem and going to the computer), I was able to discover that portion of a chip inside my computer was inoperative. The condition has previously gone undetected because the line served by the pin had not been used by other equipment previously attached to the port. I'm sure that, had I not had the tester, I would have spent several hours trying to correct what I first believed was a software problem.

First-rate Construction

The construction of the product is "first-rate." Everything is soldered, all edges are smooth, and only high-quality materials are used. The LED's are mounted behind holes in the circuit board that makes up the "chassis" of the device. The holes are silvered on the inside. This treatment enhances the brightness of the glow, and makes it easy to see from virtually any angle.

A placard is conveniently attached to the rear, and provides a wealth of information constantly needed during a configuration or trouble shooting project. A cover retains the jumper wires when the unit is not in use.

The Patch Set has the function of similar products selling for nearly three times as much. Accordingly, it qualified in my book for "best-buy" status.

I recommend that such a device be purchased and used to make a thorough analysis of the status of each pin of each RS-232 device of your system. Then, when a problem develops, you will be able to quickly determine the cause.

When your installation is complete, either the Test Set or Patch Kit can be left attached. Its LED's will give you assurance when you need it and pinpoint a problem if, and when, one develops.

The company also supplies a series of color-coded (sex) adapters, and null-modem configurations, measuring 2×1¾×½ inches. They are priced at $25.00 each. The Anything Cable is a seven foot, 25-conductor, ribbon cable with both a male and female connector on each end. You can do just about "anything" with it, for a cost of $75.00.