User`s manual

U.S. Robotics I-modem Command Reference
Testing • Page 14-6
Granting a Digital Loopback Test Request (&T4)
The &T4 option causes the I-modem to grant a remote device's request for a remote digital
loop-back test.
Canceling All Digital Loopback Test Requests (&T5)
The &T5 option cancels &T4, and the I-modem fails to recognize remote digital loopback
test requests. This is the default so that your I-modem isn't subject to another user calling
and tying up your I-modem without your permission.
Testing Using Keyboard Data (&T6)
1. Send the command AT&M0&N3S14.0=0 to prepare the I-modem for testing.
This command disables error control, Þxes the connection rate at 2400 bps, and makes
the I-modem return to Command mode
when you type the escape code (+++).
2. Establish a connection with the remote device.
3. If you haven't already done so, arrange with the remote user to cooperate with the test.
If necessary, set the remote device to acknowledge the remote digital loopback request.
For example, older U.S. Robotics modems need to be set to S16=8.