Multi-Tech Systems MT5600ZDX ユーザーズマニュアル

1. Arrange to have &T4 set on the remote test modem. This command enables the

remote modem to respond to an &T6 request for a remote digital loopback test
from the local modem.

2. Open your communications software and go into terminal mode. Type AT and

press E

NTER

; you should get an OK message. Type AT\N and press E

NTER

 to

disable error correction. Type AT+MS=9,1,9600,9600 and press Enter to set the
local modem to V.32 mode at 9600 bps.

3. Dial the remote modem and establish your online connection.

4. Type the escape sequence +++AT and press E

NTER

 to bring your modem into

online command mode.

5. Type AT&T6 and press E

NTER

. The local modem responds to this command by

transmitting an unscrambled marking signal, which causes the remote modem
to place itself in digital loopback mode. Then the local modem exits online
command mode and enters data mode.

6. Enter data from your keyboard. For this test, typing multiple uppercase U

characters is a good way to send an alternating test pattern of binary ones and
zeroes. Data received by the remote modem enters its analog receiver, is
converted to digital data, is reconverted into analog, and then is transmitted
back to your modem. Your modem passes this test if the data received on your
monitor is the same as the data entered from your keyboard.

7. To exit the test, type the escape sequence +++AT and press E

NTER

. 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 E

NTER

 to exit the test, then type ATO and

press E

NTER

 to return on line. If you wish to terminate the call, type ATH and

press E

NTER

 to hang up.

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.

Figure C–3. Local digital loopback test.