ZyXEL Communications U-336S User Manual page 145

Local Digital Loopback Test (AT&T3)
This test will loopback the digital form data demodulated from the
receiver to the input of the transmitter. During testing, all data received
from the remote modem will be returned to the remote modem. This
test is applicable when the remote modem does not provide V.54
Remote Digital Loopback capability. This test can be initiated by the
local modem when the modems are on-line.
Remote Digital Loopback Test (AT&T6)
This test will request the remote modem to do a digital loopback.
During testing, the local modem will send a remote digital loopback
request to the remote modem according to V.54. If the remote modem
supports V.54 and is programmed to grant this kind of request, it will
resend all of the received data back to the local modem. The local
terminal or computer will receive all of the data it sends out. This test is
applicable when the remote modem and local modem both provide
V.54 Remote Digital Loopback capability. This test can be initiated by
either modem when the modems are on-line.
Remote Digital Loopback with Self-test (AT&T7)
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 Remote Digital Loopback Test. In asynchronous mode,
the pattern consists of printable ASCII characters. You can see the
results on the screen. In the synchronous mode, the pattern is made up
of scrambled binary 1, and the Throughput Meter of the initiated
modem will change to a Bit Error Rate Meter. The left reader displays
accumulated bit errors and the right reader displays accumulated bits
sent. This test can be initiated by either modem when the modems are
on-line.
Diagnostics & Troubleshooting 131