Testing the Courier V.Everything Modem using AT&T n
15-5
Digital Loopback
Testing (AT&T3)
This test can help you locate a problem with a remote device or with the
telephone line. The figure below shows the data flow during Digital
Loopback (DL) testing.
1
Send the command
AT&M0&N3S14.0=0
to the modem to prepare for
testing.
This command disables error control, fixes the connection rate at 2400
bps, and makes the Courier return to command mode when you type
+++.
2
Establish a connection with the remote device
3
Send the Courier V.Everything modem the escape code,
+++
, to bring it
back to Command mode
4
Send
AT&T3
to the modem to enter Digital Loopback mode.
5
Have the remote user type a short message. It will be looped back by your
Courier V.Everything modem's transmitter for verification on the remote
user's screen. You will not see the message or any other data.
6
When the remote user has completed the test, send the escape code,
+++
, and then
AT&T0
to end the test.
Alternatively, you can end the test by sending ATH or ATZ. Be careful
because ATZ resets the modem in addition to ending the test
In any case, the Courier V.Everything modem responds OK. If the modem
sends an ERROR message, you have issued an invalid command.
7
Send
AT&M4
, unless you used ATZ.
To DTE
Transmitter
Receiver
Telco
To DTE
Transmitter
Receiver
Telco
TX
RX
Local
Remote
Summary of Contents for Courier
Page 12: ......
Page 28: ...1 14 CHAPTER 1 CONNECTING TO YOUR ISP ...
Page 36: ...3 4 CHAPTER 3 UPGRADING YOUR MODEM ...
Page 58: ...6 6 CHAPTER 6 WORKING WITH MEMORY ...
Page 64: ...8 4 CHAPTER 8 CONTROLLING EIA 232 SIGNALING ...
Page 72: ...9 8 CHAPTER 9 ACCESSING AND CONFIGURING THE COURIER V EVERYTHING MODEM REMOTELY ...
Page 80: ...10 8 CHAPTER 10 CONTROLLING DATA RATES ...
Page 96: ...12 6 CHAPTER 12 FLOW CONTROL ...
Page 108: ...13 12 CHAPTER 13 HANDSHAKING ERROR CONTROL DATA COMPRESSION AND THROUGHPUT ...
Page 112: ...14 4 CHAPTER 14 DISPLAYING QUERYING AND HELP SCREENS ...
Page 122: ...15 10 CHAPTER 15 TESTING THE CONNECTION ...
Page 142: ...17 8 CHAPTER 17 TROUBLESHOOTING ...
Page 156: ...A 14 APPENDIX A S REGISTERS ...
Page 172: ...B 16 APPENDIX B ALPHABETIC COMMAND SUMMARY ...
Page 178: ...C 6 APPENDIX C FLOW CONTROL TEMPLATE ...
Page 186: ...E 4 APPENDIX E V 25 BIS REFERENCE ...