ZyXEL Communications U-336S User Manual page 143

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