3Com NETBuilder SI Using Manual page 171

Figure 25 shows the pin assignments of the ISDN S/T cable.
Figure 25 ISDN S/T Cable
To WAN port
1 2 3 4 5 7 8
RJ-45 male (shielded)
Name Abbr. Pin
Not connected
Not connected
Transmit Data+
Receive Data+
Receive Data-
Transmit Data-
Not connected
Not connected
WAN Connector and Cables
6
NC 1
2
NC
TxD+ 3
4
RxD+
RxD- 5
6
TxD-
NC 7
8
NC
To wall outlet or NT1
1 2 3 4 5 7 8 6
RJ-45 male (shielded)
Pin Abbr. Name
1 NC Not connected
2 NC
Not connected
3 TxD+ Transmit Data+
4 RxD+
Receive Data+
5 RxD- Receive Data-
6 TxD-
Transmit Data-
7 NC Not connected
8 NC
Not connected
171