Indicator Lights

Retransmission Indicator

In the error control mode, an error occurring in the link will cause the data to be re-transmitted. At the same time, the AA LED will flash. This also indicates the quality of the line.

Dialing Indicator

The V34 LED will flash on and off for 1/2 second each to indicate that the modem is dialing. This flash will continue after dialing until a carrier is detected. Therefore, the V34 LED will also flash in leased-line modem connections when one modem is trying to handshake but the other modem is not turned on.

Handshaking And Retrain Indicator

The V34 LED will flash on and off in 1/2 second intervals to indicate that the modem is handshaking or retraining.

Line Condition Status Display

Regarding data being transmitted over telephone line circuits, there are many kinds of line impairments that can affect the data being received by the remote modem.

Your modem can measure four major line impairments. From the impairment readings, you can understand the current line condition. Your modem also logs line events over a long period, so you know what the line condition has been. We will describe these readings and logs as follows:

ONOTE: THE READINGS DISPLAYED ARE NOT MEASUREMENTS AND SHOULD ONLY BE USED AS A REFERENCE.

Signal to Noise Ratio (S/N)

This reading is expressed in 0.1 dB resolution. The higher the speed, the higher the S/N ratio required. The modem measures the S/N ratio by

132 Diagnostics & Troubleshooting

Page 146
Image 146
ZyXEL Communications U-336SA user manual Indicator Lights, Line Condition Status Display

U-336S, U-336SA specifications

ZyXEL Communications, a leading global provider of networking and cybersecurity solutions, has offered a range of products designed to cater to various connectivity needs. Among these, the U-336SA and U-336S modems stand out for their reliability and performance, particularly in the dial-up category during the heyday of internet access.

The U-336SA and U-336S modems are external devices that revolutionized the way users connected to the internet in the late 1990s and early 2000s. Designed for both home users and small businesses, these modems supported 33.6 Kbps data transfer rates, which, at the time, were considered cutting-edge. This capability allowed for reasonably swift internet browsing, email communication, and file downloads compared to earlier modems.

One notable feature of both the U-336SA and U-336S models is their plug-and-play functionality. This ease of use made them accessible to even the less tech-savvy users, allowing quick and straightforward installation. Users could connect the modems to their PCs or laptops via a standard serial interface, minimizing setup time and complexity.

Additionally, both modems were equipped with error correction and data compression technologies. The V.42 and V.42bis protocols enhanced data integrity during transmission, ensuring that users experienced fewer disruptions and greater reliability in their connecting experience. This was particularly vital for tasks like file transfers and large downloads, where data integrity was paramount.

The modems also featured compatibility with various operating systems, including early versions of Windows, which expanded their appeal to a broader audience. The U-336SA was specifically engineered as a standalone device, while the U-336S could often be used with existing computer systems, showcasing versatility in various deployment scenarios.

In terms of design, both modems were compact and lightweight, allowing for easy portability. This made them suitable for users who required connectivity on the go or in different locations.

Ultimately, the ZyXEL U-336SA and U-336S modems represent a significant technological achievement in the history of internet connectivity. Their introduction set the stage for subsequent advancements in modem technology and played a crucial role in the evolution towards broadband and high-speed internet access that we enjoy today. Their legacy endures in the foundational technologies and protocols that continue to drive modern telecommunications.