US Robotics COURIER - Remote Digital Loopback Tests (&T6, &T7)

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&T4, &T5
COURIER HIGH SPEED MODEMS
2. Bring the modem back to Command mode with the +++
escape code. Then send it the AT&T3 command. The
modem enters DL mode and the MR status light flashes.
3. The remote user should type a short message. It will be
looped back by your modem's transmitter for verification on
the remote screen. You will not see the message or any other
data.
4. When the remote user has completed the test, issue the
AT & TO command to end the test. Or send either ATH or the
command that resets the modem, ATZ. The latter two
commands end the test and hang up the modem. The
modem responds OK. If the modem sends an ERROR
message, you have issued an invalid command.
5. Reset DIP switch 9 OFF if you normally use the factory
default. Reset the modem to &M4 unless you used the reset
command, A TZ.
The &T4 option causes the modem to grant a remote modem's
request for a Remote Digital Loopback test.
The &TS option cancels &T4, and the modem fails to recognize
such a request. This is the default so that your modem isn't
subject to another user calling and tying up your modem
without your permission.
REMOTE DIGITAL LOOPBACK-&T6, &T7
This test, like the local digital loopback test, verifies the
condition of both modems and the phone link. Data flow is
shown in Figure F-3.
Local Modem
Remote Modem
Figure F-3. Data Flow During Remote Digital Loopback
The request for and granting of Remote Digital Loopback testing
requires that both modems use CCITT V.22 standard signaling.
Modem Testing F-5