3Com PC Card User Manual page 41

S23 Bit-mapped. Storable.
Bit 0. Detect RDLB (&T4 and &T5 CMD)
0 = Deny RDLB (&T5 CMD)
1 = Accept RDLB (&T4 CMD)
Bit 3,2,1. DTE port communications speed (bits/s)
0 = 300
4 = 4800
1 = 57600
5 = 9600
2 = 1200
6 = 19200
3 = 2400
7 = 38400
Note: bits 3,2 and 1 of S23 are only valid if bits 3,2 & 1 of S19 = 0.
Bit 5,4. Parity
0 = Even
2 = Odd
1 = Space / none
3 = Mark
Bit 7,6. Guard Tone (&G CMD)
0 = None
2 = 1800 Hz
1 = 550 Hz
3 = Not used
S Registers 37