Digital Loopback Test/V.54 Loop 2 (Local/Manual) - Multitech MULTIMODEM MT5600ZDX Owner's Manual

5. Your modem passes this test if the data entered from your
keyboard are the same as the data received on your monitor. If
different data is appearing on your monitor, your modem is
probably causing the problem, although it could also be your
computer. If your modem passes this test, but you are receiving
errors while On-line, the remote modem or the phone line could
be at fault.

Digital Loopback Test/V.54 Loop 2 (Local/Manual)

The Digital Loopback Test is an on-line test that loops data sent from
one modem across the phone line to another modem, then back to the
first modem. See Figure 4-2.
There are two ways to put a modem into Digital Loopback mode.
1. Locally or Manually, described here in this section.
2. Remotely or Automatically, see the following section.
Note: If you wish to abort any test in progress, enter AT&T0<CR> .
All loopback tests will operate at all speeds except 300 bps.
Disable error correction ( AT\N0&W0<CR> ) before engaging in
loopback tests. In this test the local modem is placed in Digital
Loopback mode. Data is entered and transmitted from the remote
modem (which is not in digital loopback mode), sent across the phone
line to the local modem and looped back to the remote modem.
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.
3. Type the Escape Sequence ( +++ ) which brings your modem into
Command mode, while still maintaining the pseudo On-line mode
with the remote modem.
4. Type AT&T3 from the local PC and hit ENTER. Once you receive
an OK message from your modem (if responses are enabled), the
local modem is placed in Digital Loopback mode.
Chapter 4 - Testing Your Modem
69