Multi-Tech Systems MT2834BLR, MT2834BR manual Digital Loopback Test/V.54 Loop 2 Remote/Automatic

Chapter 5 - Testing the Modem

5.3Digital Loopback Test/V.54 Loop 2 (Remote/Automatic)

In this test, your modem must be On-line with another modem set up to respond to a request for Digital Loopback. The test is as follows:

1.Enter Terminal mode.Type AT and hit ENTER. An OK message displays.

2.Dial the remote modem by entering the Dial command and the phone number, to establish On-line mode.

Note: Set the &T4 command on the remote modem prior to running test.

3.Type the Escape Sequence (+++AT<CR> or <BREAK>AT<CR>) to enter Command mode, maintaining the remote modem connection.

4.Type ATU2 and hit ENTER. The local modem transmits an unscrambled marking signal. The remote modem enters Digital Loopback mode. The local modem exits Command mode and enters pseudo On-line mode.

5.Type multiple uppercase "U" characters to send an alternating test pattern of ones and zeros. The data received by the remote modem enters the analog receiver and is converted to digital data. The data is reconverted into analog, then looped through the transmitter back to the local modem. If the data entered from the keyboard is the same as the data received on the monitor, the modem has passed the test.

Computer or Terminal	Computer or Terminal
UUUU
Local Modem	Remote Modem

Digital Analog Analog Digital

Figure 5-3. Digital Loopback Test (remote / automatic)

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