IBM Aptiva Handbook page 190

Table 15: S registers (Continued)
Register Function
S21 Originate-only, line, DTR, DCD, DSR, and Long Space Disconnect
S22 Speaker, M/B ratio and response
S23 DTE data rate, parity, and guard tone
S24 Calling tone
S25 Data Terminal Ready delay
S26 RTS to CTS delay interval
S27 Async/Sync operation, clock source, DCE speed
S28 Line speed control register
176 Appendix C: Modem information
Range/units
Bit-mapped register
Bit-mapped register
Bit-mapped register
0-100 seconds
0-255 /100ths of a second
Bit-mapped register
Default
None
None
None
None
5
1
None
None