Owner`s manual

PN 88300150

4/3/01 60

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

In this test, your modem must be On-Line with another modem that can respond to a request for Digital

Loopback, such as another MT2834MR. 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 6-2.

There are two ways to put a modem into Digital Loopback mode.

1. Locally or Manually, described here in section 6.3.

2. Remotely or Automatically, see section 6.4.

Note: The Digital Loopback Tests can only be used with the modem in Normal mode (error correction

off).

Figure 6-2. Digital Loopback Test (local/manual)

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. Disable Error Correction by typing the &E0 command.

2. Go into Terminal mode. Type AT and hit ENTER; you should get an OK message.

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

mode.

4. Type the Escape Sequence (+++AT<CR> or <BREAK>AT<CR>) which brings your modem into

Command mode, while still maintaining the pseudo On-line mode with the remote modem.

5. Type ATU3 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.

6. Data is typed from the remote keyboard. For this test, typing multiple upper case "U" characters is a

good way to send an alternating test pattern of ones and zeros. The data received by the local

modem will enter its analog receiver, be converted to digital data, be reconverted into analog, and

then looped through its transmitter back to the remote modem. Your modem passes this test if the

data entered from the remote keyboard is the same as the data received on the remote monitor.

7. When testing is complete, you may end the test by typing an Escape Sequence (+++AT<CR> or

<BREAK>AT<CR>) to bring your modem into 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

AT0 and hit ENTER. If you wish to terminate the call, type ATH and hit ENTER to hang up.