3Com 10014299 manual Internal loopback/external loopback are disabled by default, Detect dcd

	Synchronous Serial Interface 127
Enable level detection for the synchronous serial	detect dsr-dtr
interface.
Disable level detection for the synchronous serial	undo detect dsr-dtr
interface.

Level detection is enabled for the synchronous serial interface by default.

9Enable or disable data carrier detection

By default, when the system decides whether the synchronous serial interface is in UP status or DOWN status, it detects the DSR signal, DCD signal and whether the interface connects a cable at the same time. Only when the three signals are effective, will the system regard the interface is in UP status, otherwise, in DOWN status. If data carrier detection is disabled for the synchronous serial interface, the system will not detect the DCD signal.

Please use the following commands in the view of the synchronous serial interface.

Table 118 Enable or disable data carrier detection for the synchronous serial interface

Operation	Command
Enable data carrier detection for the synchronous serial	detect dcd
interface.
Disable data carrier detection for the synchronous serial	undo detect dcd
interface.

Data carrier detection is enabled for the synchronous serial interface by default.

10Set the synchronous serial interface to work in full duplex or half duplex mode

To operate with some devices working in half-duplex mode, the synchronous serial interface can be configured to work in half-duplex mode.

Please make the following configurations in synchronous serial interface mode.

Table 119 Set the synchronous serial interface to work in full duplex or half duplex mode

Operation	Command
Set the synchronous serial interface to work in half	reverse-rts
duplex mode
Set the synchronous serial interface to work in full	undo reverse-rts
duplex mode

By default, the synchronous serial interface works in full duplex mode.

11Enable or disable internal loopback/external loopback

To perform special function test, the internal loopback/external loopback are enabled for the synchronous serial interface.

Please use the following commands in the view of the synchronous serial interface.

Table 120 Enable/disable internal loopback/external loopback for the synchronous serial interface

Operation	Command
Enable the internal loopback/external loopback for	loopback
the synchronous serial interface.
Disable the internal loopback/external loopback	undo loopback
for the synchronous serial interface.

The internal loopback/external loopback are disabled by default.