Multitech MULTI MODEM II MT5600BA - Manual (Page 95)

C Loopback Tests
89
MultiModemII User Guide
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 E NTER 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 com-
mand mode and enters data mode.
6. Enter data from your keyboard. For this test, typing multiple uppercase U char-
acters 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 mes-
sage. If you wish to stay on line with the remote modem for normal data trans-
mission, 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.
Note: You can also start and stop a remote digital loopback test by using the front
panel LCD and buttons. See “Diagnostic Options Trunk” in Chapter 3.
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 it-
self 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.
Computer or Terminal
UUUUUUUUUUU
UUU
Local MultiModem Remote MultiModem Computer or Terminal
Digital Analog Digital Analog
AT&T3
OK
Figure C-3. Local digital loopback test.