Command Echo Problems

3.You may have typed the commands when your modem was in data state instead of the command state. To switch from data state to command state, type the escape sequence code +++. To return to the data state, type ATO and press Enter.

Problem

You typed an AT command, but did not receive an OK or 0 result code.

Solutions

1.Your communications software may be using a different COM port than your modem. Be sure both the software and your modem are addressing the same COM port.

2.The E0 and Q1 commands may be in effect, disabling echo and result codes. To verify this in terminal mode, type AT&V0 and press Enter with the modem in command state to view the currently active settings. To enable echo and result codes, type AT E1 Q0 and press Enter.

3.You may have typed the commands when your modem was in the data state instead of the command state. To switch from data state to command state, type the escape sequence code +++. To return to data state, type ATO and press Enter.

Problem

You receive the ERROR result code after typing an AT command.

Solution

You may have typed a command that is not recognized by your modem or communications software.

Problem

You do not see any typed characters on your computer screen.

136 Diagnostics & Troubleshooting

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.

ZyXEL Communications U-336SA user manual Command Echo Problems

Models: U-336S U-336SA