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SERIES II INTELLIGENT DATA/FAX MODEMS
8.4 Digital 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, such as another Series II
Modem. With the Modem, this ability to respond is controlled by the
&T command. AT&T4 enables the response to Digital Loopback Test
(remote/automatic). AT&T5 disables the response. The modem
defaults to disable on power up, so this must be changed on the remote
modem before the modem will respond to a request for the Digital
Loopback Test (remote/automatic).
Initiate the Digital Loopback Test (remote/automatic) with the ATU2
command which automatically places the remote modem in digital
loopback mode. Data from your computer or terminal are transmitted
through your modem, and over the phone line to the remote modem,
where they are then looped back to your modem. See Figure 8-3.
The test procedure is as follows:
1. Go into Terminal mode. Type AT and hit ENTER; you should get
an OK message.
2. Dial the remote modem by entering the Dial command and the
phone number, to establish On-line mode.
Note: The &T4 command must be set on the remote modem to
run this test.
Figure 8-3. Digital Loopback Test (remote/automatic)
UUUUU
UUUUU
Computer
or Terminal
Computer
or Terminal
Local Series II
Modem
Remote Series II
Modem
Type AT in Terminal mode; hit ENTER;
dial remote modem; establish On-line
mode; enter escape sequence; type ATU2
and hit ENTER
digital
analog
analog
digital