3Com Courier Reference page 155

Register Default Function
S70 0 Bit-mapped Register. See the beginning of this appendix for
information about setting bit-mapped registers.
Bit
0
1
2
3
4
Value Result
1 Enable recognition of Ring A
2 Enable recognition of Ring B
4 Enable recognition of Ring C
8 Enable recognition of Ring D
16 Enable recognition of Ring E
A complete list of S-Registers A-13