3Com 10014299 manual E1-F Interface, Choice for E1 access, Them into multiple channel sets

	E1-F Interface 139
Set the frame format of CT1/PRI interface	frame-format { sf esf }
Restore the frame format of CT1/PRI interface	undo frame-format
to the default value

By default, the frame format of CT1/PRI interface is ESF.

8Enable/disable internal loopback/external loopback

The interface needs to be set to internal loopback or external loopback when during the test on some special functions.

Perform the following configurations in CT1/PRI interface view.

Table 146 Enable/disable the internal loopback/external loopback of the CT1/PRI

Operation	Command
Enable the internal loopback/external loopback of the	loopback { remote local }
CT1/PRI
Disable the internal loopback/external loopback of the	undo loopback { remote
CT1/PRI	local }

By default, the functions of internal loopback and external loopback are disabled on the CT1/PRI interfaces.

Display and Debug Perform the following configurations in all views to display the status and related CT1/PRI Interface information of the CT1/PRI interface, so as to monitor and maintain it.

Table 147 Display and debug CT1/PRI interface

Operation	Command
Display the operating status of the CT1/PRI	display	controller t1
interface	interface-number
Display the operating status of the channel set	display	interfaces serial
or pri set	interface-number:number

Generally, CT1/PRI interfaces are applied to the dedicated line and dial-up services. For the typical configuration example and troubleshooting, refer to the configurations of protocols at each layer and dialing configurations in this manual.

E1-F Interface	E1-F interface is fractional E1 interface, and it is respectively simplified CE1/PRI
	interface. If there is no need to use multiple channel sets or if ISDN PRI is not
	necessary in an E1 application, it is too much to use CE1/PRI interface. At this time,
	E1-F interface is more than enough for meeting the simple E1 access
	requirements. Compared with CE1/PRI interface, E1-F interface is a nice low-cost
	choice for E1 access.
	Compared with CE1/PRI interfaces, E1-F interface has the following features:
	■ When working in framed mode, E1-F interface can only bind time slots into
	one channel set, but CE1/PRI interface can group timeslots randomly and bind
	them into multiple channel sets.
	■ E1-F interface does not support PRI operating mode.
	E1-F interface can work in both framed and unframed modes.
	When it works in unframed mode, it is a timeslot-less interface of 2048kbps data
	bandwidth. In this case, it is logically equivalent to a synchronous serial interface,