Chapter 13 - Diagnostics & Troubleshooting
13-2
Resetting The Modem
If you change the modem's setting and cannot get it back, or if you just want to get
back to the factory default state, the following reset procedure will reset the
modem to the factory state. This procedure also causes the modem to run a self-
test. It is a good way to test the modem hardware.
1. Hold the DATA/VOICE key down while powering up the modem. Hold it for
less than 10 seconds otherwise the modem will go to firmware update kernel
execution.
2. The Omni 288S will run a continuous analog loopback self-test. Printable
characters will be shown on the terminal connected to the modem's DTE port.
3. The V34, CD, DSR, CTS, RXD, EC, and SQ LEDs should be ON. If not,
there is a hardware problem. Contact the nearest service center for help. If
SQ flashes, the number of flashes indicates the error number corresponding to
the error message in the table above.
4. The modem will be reset and will run a self-test. Printable characters will be
shown on the computer screen. The SQ LED should be continuously ON. If
the LED flashes, the number of flashes indicates the error number
corresponding to the error message listed in the table above.
5. This hardware reset procedure will reset the supervisor password back to
the default ZyXEL. But if you set S35.6=1 in profile 0 the supervisor
password is protected and not reset.
Loopback Tests
The Analog Loopback Test (with Self -Test), Local Digital Loopback Test,
Remote Digital Loopback Test (with Self-Test) can all be initiated with AT
commands from the terminal. Use the AT&T0 command to terminate the test.
Analog Loopback (AT&T1)
This test can check almost every part of the modem and the RS-232 cable except
the telephone line outgoing interface. During Analog Loopback testing, data from
the terminal or computer is sent through an RS-232 cable into the modem's
transmitter and is modulated to an analog signal. Then it is looped back to the
receiver, demodulated to digital form and sent through the RS-232 cable back to
the terminal or computer's screen. You can tell if anything is wrong by looking at
the screen. The screen should show the data you have sent to the modem. This test
can only be initiated while the modem is off-line.
Analog Loopback with Self-test (AT&T8)
This test generates data from the modem itself instead of input data from the RS-
232 interface. The data will go through the same path as it would with the Analog
Loopback Test. In asynchronous mode, the pattern consists of printable ASCII