63
Appendices
Local Digital Loopback Test (V.54 Loop 2)
The local digital loopback test is identical to the remote digital loopback test with one exception.
Instead of using your modem to signal a remote modem to place itself in digital loopback mode, your
modem is placed in digital loopback mode while the remote modem is not. Data is entered and
transmitted from the remote modem, sent across the phone line to your modem, and looped back to
the remote modem.
UUUUUUUUU
UUUUU
Computer or Terminal
Local MultiModem
Remote MultiModem Computer or Terminal
Digital
Analog
Digital
Analog
AT&T3
OK
Figure C-3. Local digital loopback test
Test Procedure
1. Open your communications software and go into terminal mode. Type
AT
and press ENTER;
you should get an
OK
message. Type
AT\N
and press ENTER to disable error correction.
2. Dial the remote modem and establish your online connection.
3. Type the escape sequence
+++AT
and press ENTER to bring your modem into online
command mode.
4. Type
AT&T3
and press ENTER. Once you receive an
OK
message from your modem (if
responses are enabled), your modem is placed in digital loopback mode.
5. Have someone enter data from the remote keyboard. For this test, typing multiple uppercase
U
characters is a good way to send an alternating test pattern of binary ones and zeros. The
data received by your modem enters its analog receiver, is converted to digital data, is
reconverted into analog, and then is transmitted back to the remote modem. Your modem
passes this test if the data received on the remote monitor is the same as the data entered
from the remote keyboard.
6. To exit the test, type the escape sequence
+++AT
and press ENTER. This puts the modem in
online command mode. The modem should respond with an
OK
message. If you wish to stay
on line with the remote modem for normal data transmission, type
AT&T
and press ENTER to
exit the test, then type
ATO
and press ENTER to return on line. If you wish to terminate the
call, type
ATH
and press ENTER to hang up.
Summary of Contents for MT5634MU
Page 1: ...Model MT5634MU Portable USB Modem User Guide ...
Page 5: ...Chapter 1 Introduction and Description ...
Page 12: ...12 MultMobileUSB User Guide ...
Page 13: ...Chapter 2 Installation ...
Page 30: ...30 MultiMobileUSB User Guide ...
Page 31: ...Chapter 3 AT Commands S Registers and Result Codes ...
Page 47: ...Chapter 4 Remote Configuration ...
Page 50: ...50 MultiMobileUSB User Guide ...
Page 51: ...Chapter 5 Troubleshooting ...
Page 55: ...Appendices ...