Table of Contents
Advertisement
Tests
Remote Digital Loopback
Remote Digital Loopback, illustrated in
commanded with AT commands. The loopback can be commanded only after a call is established
and both ends are in data mode. In this loop, the de-scrambled received data from the demodulator
at the remote end is coupled to the remote transmitter input for transmission back to the local end.
This test is not operational when the modems are passing data at 300 bps.
Note
This test cannot be performed if the remote modem is commanded to ignore a remote digital loopback
command.
If the modems are operating at V.22 bis speeds and the local modem issues the RDL command to a
remote unit configured to ignore the remote loopback command the resulting condition will cause the
local modem to drop the connection.
Table 6-4
Remote Digital Loopback
Step
1.
Establish data communications with a remote modem.
2.
Check with the remote attendant that the remote modem will accept Remote Digital Loopback commands.
3.
To start the test, type the escape sequence (
(enter). If modem responds with an error message, type:
AT&T6
mode, then re-enter the command.
4.
The modem flashes the TM LED while it is setting up the test, then lights the TM LED while the test is
running.
5.
Enter data at the local DTE. Compare data that was entered at the DTE with the data that is looped back
and displayed by the DTE. If errors occur frequently, a problem may exist in the local or remote modems,
local DTE, local DTE-to-modem connection, or the communication line. For fault isolation refer to
6-1.
6.
To end the test, type the escape sequence (
AT&T0
(enter) then type ATO (enter) to go back on line.
NOTE: Any attempt to terminate the test at the remote modem by using the AT&T0 command causes the modem
to disconnect from the line.
NOTE: CTS at the remote modem drops low during the test.
TM LED is lit on both modem front panels during the test.
DTE
HELLO
INTER-
FACE
........
.......
Figure 6-5
060R122-000
Issue 15
AT Command Mode
+++
) and, after the modem is in the command mode, type:
+++
) and, after the modem is in the command mode, type:
TX
TX
DRIVER
LOGIC
Communications
Line
RX
ANALOG
LOGIC
RECEIVER
local modem
Remote Digital Loopback Data Path
SpectraComm Dual V.34 Modem
Installation and Operation
Remote Digital Loopback
Figure
6-5, is controlled at the local end. It can be
(enter), which resets the test
AT%T0
RX
ANALOG
LOGIC
RECEIVER
TX
TX
DRIVER
LOGIC
remote modem
Figure
:
DTE
INTER-
HELLO
FACE
........
.......
6-7
Advertisement
Table of Contents
