X.25 In The D Channel - ASCOM Ascotel 2025 System Manual

6.4

X.25 in the D Channel

The public ISDN network provides transitions from the D channel of an ISDN
access to X.25 data networks (X.31 Case B)
mitting packet-based data over the D channel at a maximum rate of 9,600 bit/s
(with low priority) in addition to protocol messages (example: automatic teller
machines, credit card terminals).
The advantage of data transmission over the D channel is that voice / data calls
can be made simultaneously over the allocated B channels.
X.25
Fig. 2.108: X.25 transmission via the D channel
For information concerning the wiring and the availability of the service at the
interfaces, refer to "Part 4: Installation".
Tips on using X.25
• The digital switching of the public exchange must be capable of forwarding
packet-switched data in the D channel to the X.25 network.
• Avoid excessive loads such as those that can occur through continuous data
transmission or extensive backups.
• Errors can be prevented by reducing the data rate or by distributing the load
over several X.25 channels.
• The S bus must be configured in the system to the ETSI bus.
• X.25 data can be transmitted simultaneously over the D channel and two B
channels each of the S/T ports.
1)
Only available in certain countries.
HBT_20321104_02/B0_en
ascom
1)
. It provides the capability of trans-
T
ISDN PBX
P-P
haz0140aaenc0
Ascotel 2025/2045/2065
X.25
terminal
V.24
S
P-MP
X.25-D
Terminal Adapter
Data Services 2.219