ZyXEL Communications IP PBX X6004 - Manual (Page 168)

Chapter 6 Server
X6004 User’s Guide
168
6.12 Network Technical Reference
This section contains background material relevant to the Server screens.
ISDN Overview
ISDN (Integrated Service Digital Network) is a circuit-switched telephone network
system. In ISDN, there are two types of channels: B-channels and D-channels.
ISDN allows digital transmission of voice, video and data over ordinary telephone
copper wires using B-channels with 64 kbps bandwidth. D-channels are mainly
used for signaling and control with 16 kbps or 64 kbps bandwidth depending on
service levels.
There are two service levels in ISDN as follows.
• BRI (Basic Rate Interface): BRI contains two 64 kbps B channel and one 16
kbps D channel (2B+1D). A BRI user can have up to 128 kbps service.
• PRI (Primary Rate Interface):
• North America and Japan use 23B+1D, with a total bandwidth of 1.544 Mbps
(T1).
• Europe, Australia and most of the rest of the world use the slightly higher
capacity E1 which is 30B+1D with a total bandwidth of 2.048 Mbps.