Installing and Administering PPP

Appendix A 155
Modem Connections
Dial Up Modems
S Registers
S registers are settings stored in the modem's memory. The S register
format is Sr=n where r is the register's number and n is the register's
value. For example, S0=1 indicates the modem should answer an
incoming call after the first ring. S7=30 tells the modem to wait 30
seconds after dialing before establishing a connection.
There are 256 possible S registers, although some are reserved and many
are not used at all. Each manufacturer has a proprietary license to use S
registers as it likes, but some registers are fairly consistent. Some are
shown in the table below, although there is no guarantee they will match
your modem's settings. Review your system or modem documentation to
determine the meanings and values of your modem's S registers.
&Wn Save current modem settings as n.
\Nn Select error control mode.
\Qn Select serial port flow control.
S Register Description
S0 In auto answer mode, which ring to answer on
S1 Ring counter
S2 Escape character; default is +
S3 Carriage return character; default ASCII 13
S4 Line feed character; default is ASCII 10
S5 Backspace character; default is ASCII 18
S7 Seconds to wait after dialing to establish a connection
S9 Tenths of seconds to wait before issuing carrier detect
signal
S46 Select error control and data compression
Common
Commands
Description