Digital Loopback-&T3; Digital Loopback-& T3 - US Robotics COURIER User Manual

COURIER HIGH SPEED MODEMS
&T2
resets the modem, ATZ. Both of the latter end the test and
hang up the modem.
The modem hangs up and returns a three-digit code,
followed by OK A code of 000 indicates no errors were
found. A code of 255 indicates 255 or more errors. An
ERROR message indicates that you issued an invalid
command.
5.
If there were no errors, reset the modem to &M4 for error
control unless you issued the ATZ command.
This option is reserved.
DIGITAL LOOPBACK-&T3
If your modem has passed the AL test, this test can help you
locate a problem with a remote modem or the telephone channel.
Figure F-2 shows the data flow during DL testing.
Local Modern
Remote Modem
Figure F-2. Data Flow During Digital Loopback
NOTE: This test requires the modem to establish a connection
and return to online-command mode in response to the +++
escape code. DIP switch 9 must be set ON so that the modem
does not hang up on receipt of the escape code. After you
change the switch, issue ATZ to the modem to initiate the new
setting.
As with AL testing, HST and Dual Standard modems should be
tested at 2400 bps or lower.
1. Set the modem to &MO, to disable error control. HST and
Dual Standard modems should be set to 2400 bps or lower to
avoid asymmetrical modulation at higher speeds. Establish
a connection with the remote modem.
F-4 Modem Testing
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