Toshiba Tecra A8, SATELLITE PRO A120 S1 Ring counter, S2 AT escape character (user defined), S3 Command line termination character (user defined), S4 Response formatting character (user defined)

D-2 User’s Manual
S-registers
Range: 0-255
Default: 0
Units: rings
S1 Ring counter
This register is read only. The value of S1 is incremented with
each ring. If no ring occurs over a six-second interval, this register
is cleared.
Range: 0-225
Default: 0
Units: rings
S2 AT escape character (user defined)
This register determines the ASCII values used for an escape
sequence. The default is the + character. The escape sequence
allows the modem to exit data mode and enter command mode
when on-line. Values greater than 127 disable the escape
sequence.
Range: 0-255, ASCII decimal
Default: 43
Units: ASCII
S3 Command line termination character (user defined)
This register determines the ASCII values as the carriage return
character. This character is used to end command lines and result
codes.
Range: 0-127, ASCII decimal
Default: 13 (carriage return)
Units: ASCII
S4 Response formatting character (user defined)
This register determines the ASCII value used as the line feed
character. The modem uses a line feed character in command
mode when it responds to the computer.
Range: 0-127, ASCII decimal
Default: 10 (line feed)
Units: ASCII