Huawei Quidway AR 28 Series Installation Manual page 55

Quidway AR 28 Series Routers Installation Manual
Caution:
The baud rate should not exceed 64kbps when the V.24 cable operates in synchronous
mode.
DTE and DCE
Synchronous serial interface can operate in both DTE and DCE mode. For two devices
connected directly, one should operate in DTE mode, and the other should operate in
DCE mode. The device at the DCE side provides a synchronous clock and specifies the
transmission rate, while the device at the DTE side accepts the synchronous clock and
communicates at the specified baud rate. Usually, the router serves as a DTE device.
To determine whether the device connected to the router is a DTE or DCE, please refer
to the manual that came with the device. Also the following table will be helpful in
identifying DTE and DCE. Usually, the PC or Router serves as a DTE device and the
Modem, Multiplexer or CSU/DSU serves as a DCE device.
In general, the asynchronous serial interface is connected to an external Modem or a
Terminal Adapter (TA) to work as the dial-up interface. In this case, it is unnecessary to
determine whether the device is DTE or DCE, and just choose an appropriate baud
rate.
For the operating mode configuration of the synchronous/asynchronous serial interface,
please refer to VRP3.4 Operation Manual.
2) Synchronous/asynchronous serial interface cable
The WAN interface of the router (except for the AR28-12) is a DB-50 receptacle. Proper
connection cable needs to be selected for the protocol applied. By far, four types of
synchronous/asynchronous serial interface cables are available. At one end of these
four types of cables is a DB-50 connector, and at the other end (network end) is a
connector that can be one of the following depending on cable type:
V.24 (RS232) DTE cable: DB-25 (male) connector
V.24 (RS232) DCE cable: DB-25 (female) connector
V.35 DTE cable: 34PIN (male) connector
V.35 DCE cable: 34PIN (female) connector
The following figures show all these cables.
V.24 (RS232) DTE cable assembly
Huawei Technologies Proprietary
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Chapter 4 Installation of the Router