8 pin RJ45 (8P8C) female connector at the device.
8 pin RJ45 (8P8C) male connector at the cable.
ISDN (Integrated Services Digital Network) carries voice and data digitally over the telephone network. The Basic Rate Interface (BRI), or basic rate access, provides two 64 kbit/s bearer (B) channels plus one 16 kbit/s signalling (D) channel — the 2B+D structure, 144 kbit/s of payload. Its S/T reference-point interface, defined by ITU-T I.430, uses an 8-pin RJ-45 (8P8C) wired to ISO/IEC 8877: one pair transmits and one receives, with two further pairs available for optional power.
| Pin | Signal | Polarity |
|---|---|---|
| 1 | Power Source/ Sink 3 | + |
| 2 | Power Source/ Sink 3 | - |
| 3 | Transmit/ Receive | + |
| 4 | Receive/ Transmit | + |
| 5 | Receive Transmit | - |
| 6 | Transmit/ Receive | - |
| 7 | Power Source/ Sink 2 | - |
| 8 | Power Source/ Sink 2 | + |
Notes
- Pins 3 & 6 and pins 4 & 5 are the two signal pairs; which pair is transmit and which is receive depends on viewpoint, as the roles swap between the terminal (TE) and network-termination (NT) ends — hence the “transmit/receive” labelling.
- Pins 1 & 2 and pins 7 & 8 carry optional power (power source/sink) and may be left unconnected.