The command &T7 starts a Remote Digital Loopback with Self-Test in accordance with
CCITT Recommendation V.54. During the test phase, an internally generated data pattern
of alternating ones and zeros at the selected bit rate is applied to the scrambler. An error
detector capable of identifying errors is connected to the output of the descrambler. At the
end of the test a three-digit error count from 0 to 255 is displayed. Both modems must be
connected before the test can start.
Test &T7 example:
+++
Escape
OK
Modem
Acknowledges
ATS18=0&T7
Start test
AT&T0 End
Test
000
Zero
errors
OK
Test
acknowledgement
The command &T8 starts a Local Analog Loopback with Self-Test in accordance with
CCITT Recommendation V.54. During the test, an internally generated data pattern of
alternating ones and zeros at the selected bit rate is applied to the scrambler. An error
detector capable of identifying errors is connected to the output of the descrambler. At the
end of the test a three-digit error count from 0 to 255 is displayed. If the modem is on line
when the test starts, carrier will be lost. This test is useful for checking the local modem
transmit and receive circuits.
Test &T8 example:
ATS18=0&T8
Start test
AT&T0 End
test
000
No
errors
OK
Acknowledgement
(&Wn) Write Configuration to NVRAM
The &Wn command saves a subset of the S registers in one of two profiles in NVRAM.
&W or &WO stores the current configuration in the first profile. &W1 stores current
parameters in the second. The first profile is restored automatically whenever the modem
is turned on, or upon issuing the Z or ZO command. The second profile may be restored
by the Z1 command. Registers saved are: SO, S14, S18, S21, S22, S23, S25, S26 and S27.
Note: If the &Wn command is issued while in the escape state, an ERROR message will
be returned, and the current configuration will not be saved.
