User`s manual

U.S. Robotics I-modem Command Reference
Testing • Page 14-7
4. Send the I-modem the AT&T6 com-mand. The I-modem enters remote digital loopback
mode, and, if the I-modem is an external model, the MR status light ßashes.
5. Type a short message. It will be looped back to your I-modem by the remote device and
to your screen for veriÞcation. (The remote user will not see your data.)
6. Send the escape code, +++, and then AT&T0 to end the test.
Alternatively, you can end the test by sending ATH, ATZ, or ATZ! Be careful, because
ATZ and ATZ! reset the I-modem in addition to ending the test.
If you issue an invalid command, the I-modem sends an ERROR message. If you set
Register S18, the I-modem automatically ends the test when the test timeout is reached.
Data errors indicate a problem with the remote device or with the phone link.
7. Send AT&M4, unless you used a reset command (ATZ or ATZ!).
Testing Using a Built-in Test Pattern (&T7)
This test option causes the I-modem to perform a remote digital loopback test by sending
a built-in test pattern. An internal error detector counts any errors and, when the test is
ended, sends the number of errors or 000 (no errors) to the screen.