IBM Aptiva Handbook page 191

Table 18: S registers
Register Function
S28 V.34 modulation enable/disable
0 Disabled
1-255 Enabled
S35 Data calling tone
0 Disabled
1 Enabled
S37 Dial line rate
0 Maximum modem speed
1 Reserved
2 1200/75 bps
3 300 bps
4 Reserved
5 1200 bps
6 2400 bps
7 4800 bps
8 7200 bps
9 9600 bps
10 12000 bps
11 14400 bps
12 16800 bps
13 19200 bps
14 21600 bps
15 24000 bps
16 26400 bps
17 28800 bps
18 31200 bps
19 33600 bps
Range / units Default
1
0
0
S registers 175