12-6
C
HAPTER
12: H
ANDSHAKING
, E
RROR
C
ONTROL
, D
ATA
C
OMPRESSION
,
AND
T
HROUGHPUT
.
Example:
Sending
AT&M4
allows your modem to operate in Normal Mode
is an ARQ connection can’t be made.
Error control is available for calls at 1200 bps and above. It can be
disabled, although high-speed calls (9600 bps or higher) should always
be under error control. The operations defined in an error-control
protocol include:
■
Establishing compatibility.
■
Formatting data frames.
■
Detecting errors using Cyclic Redundancy Checking (CRC).
■
Retransmitting corrupt data frames.
The Business Modem is set at the factory to try for an error-control
connection and, if that isn't possible, to proceed with the call in Normal
mode. This means that &M4 is set.
For your modem to
Command
Have no error control (Normal Mode)
Due to the nature of phone line channels, this is never
recommended for analog calls above 2400 bps
AT&M0
Operate in Normal mode if an ARQ connection can’t be
made (Normal/ARQ mode)
AT&M4
Hangs up if it can’t make an ARQ connection (ARQ
Asynchronous Mode)
AT&M5
Summary of Contents for OfficeConnect 56K Business
Page 14: ...4 ABOUT THIS GUIDE ...
Page 32: ...1 18 CHAPTER 1 CONNECTING TO YOUR ISP ...
Page 42: ...3 6 CHAPTER 3 MODES OF OPERATION ...
Page 64: ...7 4 CHAPTER 7 CONTROLLING EIA 232 SIGNALING ...
Page 72: ...8 8 CHAPTER 8 CONTROLLING DATA RATES ...
Page 80: ...9 8 CHAPTER 9 ACCESSING AND CONFIGURING THE BUSINESS MODEM REMOTELY ...
Page 96: ...11 6 CHAPTER 11 FLOW CONTROL ...
Page 108: ...12 12 CHAPTER 12 HANDSHAKING ERROR CONTROL DATA COMPRESSION AND THROUGHPUT ...
Page 112: ...13 4 CHAPTER 13 DISPLAYING QUERYING AND HELP SCREENS ...
Page 124: ...14 12 CHAPTER 14 TESTING THE CONNECTION ...
Page 132: ...15 8 CHAPTER 15 TROUBLESHOOTING ...
Page 162: ...B 14 APPENDIX B ALPHABETIC COMMAND SUMMARY ...
Page 168: ...C 6 APPENDIX C FLOW CONTROL TEMPLATE ...
Page 210: ...14 GLOSSARY ...