14-6
C
HAPTER
14: T
ESTING
THE
C
ONNECTION
Remote Digital
Loopback Testing
(AT&T6, AT&T7)
The remote digital loopback test, verifies the condition of both devices
and of the phone line. Data flow is shown in the figure below.
Data Flow During Remote Digital Loopback.
The request for and granting of remote digital loopback testing requires
that both devices use ITU-T V.22 standard signaling. If the remote device
does not have the capability or is not set to respond (with
AT&T4
), you will
get an ERROR result code.
There are two remote digital loopback options.
Example:
Sending
AT&T6
will verify keyboard data sent to the modem by
returning it over the phone lines and displaying it on your screen.
Granting a Digital
Loopback Test
Request (AT&T4)
Using
AT&T4
causes the Business Modem to grant a remote device's
request for a remote digital loop-back test.
Canceling All Digital
Loopback Test
Requests (&T5)
Using
AT&T5
cancels
AT&T4
, and the Business Modem fails to
acknowledge remote digital loopback test requests. This is the default so
that your Business Modem isn't subject to another user calling and tying
up your Business Modem without your permission.
If you want to Command
Send keyboard data to the modem and verify it when it is
returned over the phone lines and to your screen
AT&T6
Have the modem send its internal test pattern and return
an error count to your screen
AT&T7
