S0 bus

S0 bus (S/T or just S-bus) allows up to 8 ISDN devices. if one device is connected (I.E.: NT-1), the theoretical cable run is 1km, but is limited to 150m for 8 devices

RJ45 pinout should be

1. power source or sink 3 +
2. power source or sink 3 -
3. transmit positive
4. transmit negative
5. receive positive
6. receive negative
7. power sink 2 -
8. power sink 2 +

Source: http://ckp.made-it.com/isdn.html