15-6
C
HAPTER
15: T
ESTING
THE
CONNECTION
Remote Digita
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 Courier V.Everything 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 Courier V.Everything modem fails to
acknowledge remote digital loopback test requests. This is the default so
that your Courier V.Everything modem isn't subject to another user
calling and tying up your Courier V.Everything modem without your
permission.
To DTE
Transmitter
Receiver
Telco
To DTE
Transmitter
Receiver
Telco
TX
RX
TX
RX
Local
Remote
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
Содержание Courier
Страница 12: ......
Страница 28: ...1 14 CHAPTER 1 CONNECTING TO YOUR ISP ...
Страница 36: ...3 4 CHAPTER 3 UPGRADING YOUR MODEM ...
Страница 58: ...6 6 CHAPTER 6 WORKING WITH MEMORY ...
Страница 64: ...8 4 CHAPTER 8 CONTROLLING EIA 232 SIGNALING ...
Страница 72: ...9 8 CHAPTER 9 ACCESSING AND CONFIGURING THE COURIER V EVERYTHING MODEM REMOTELY ...
Страница 80: ...10 8 CHAPTER 10 CONTROLLING DATA RATES ...
Страница 96: ...12 6 CHAPTER 12 FLOW CONTROL ...
Страница 108: ...13 12 CHAPTER 13 HANDSHAKING ERROR CONTROL DATA COMPRESSION AND THROUGHPUT ...
Страница 112: ...14 4 CHAPTER 14 DISPLAYING QUERYING AND HELP SCREENS ...
Страница 122: ...15 10 CHAPTER 15 TESTING THE CONNECTION ...
Страница 142: ...17 8 CHAPTER 17 TROUBLESHOOTING ...
Страница 156: ...A 14 APPENDIX A S REGISTERS ...
Страница 172: ...B 16 APPENDIX B ALPHABETIC COMMAND SUMMARY ...
Страница 178: ...C 6 APPENDIX C FLOW CONTROL TEMPLATE ...
Страница 186: ...E 4 APPENDIX E V 25 BIS REFERENCE ...