Multitech MultiModem DSVD MT5600DSVD, User Manual

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MultiModemDSVD User Guide C Loopback Tests
66
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 characters received on your monitor
are the same as 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.
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
Test procedure
1. Open your communication 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 dis-
able error correction. Type AT+MS=9,1,9600,9600 and press E
NTER
to set the lo-
cal modem to V.32 mode at 9600 bps.
2. Dial the remote modem and establish your online connection.