Huawei Technologies Proprietary 
4-12 
 
Figure 4-11 AUX cable assembly 
III. Connection of the AUX cable 
Follow these steps to connect the AUX cable: 
Step 1: Plug the RJ-45 connector of the AUX cable into the AUX port of the router. 
Step 2: Connect the DB-25 or DB-9 connector of the AUX cable to the serial interface of 
the analog Modem. 
In general, the AUX port is used for remote configuration or dial-up backup. The local 
Modem is first connected to the remote Modem through PSTN, and then to the remote 
device.  
4.8.2  Connecting WAN Interface to DSU/CSU 
I. Connecting synchronous/asynchronous serial interface to DSU/CSU 
1)  Introduction to the synchronous/asynchronous serial interface 
The fixed WAN interface of Quidway AR 28 Series Router is a 
synchronous/asynchronous serial interface, which is usually used for the connection 
with a WAN device, such as a Modem or CSU/DSU. It can operate in the 
synchronous/asynchronous mode or DTE/DCE mode, depending on the application. 
For the attributes of the interface, please refer to 
Table 4-8 
Table 4-8 Attributes of the synchronous/asynchronous serial interface (DB-28) 
Description 
Attribute 
Synchronous  Asynchronous 
Connector   DB-28 
V.24 
V.35/RS449/ 
X.21/RS530 
Interface standard 
and operating 
mode 
DTE/DCE DTE/DCE 
RS232 
Minimum baud rate 
(bps) 
1200 1200  300 
Maximum baud 
rate (bps) 
64 k  2.048 M  115200