Cabletron Systems CSMIM-T1 manual Describes the arguments for T1loopback, Argument Description

T-1 Commands

T1_loopback

The superuser T1_loopback command places the T-1 engine into loopback mode. None of the loopback conditions persist through a power down or reboot. A major consideration to those using the T-1 service must be made before using this command since it will completely disrupt the T-1 service. To switch between two different types of loopback, the first loopback must be cancelled before specifying the second loopback.

The syntax for the T1_loopback command is:

T1_loopback [ none line payload local ]

Table 4-5 describes the arguments for T1_loopback.

Table 4-5 Arguments for the T1_Loopback Command

Argument	Description
None	No loopback. This is the default. If the T1_loopback
	command is initiated with no parameters, then none is
	assumed. It cancels any user specified loopbacks.
Line	Line loopback provides the network a means to test the
	T-1 circuit for single ended fault isolation. The line
	loopback regenerates the DS1 signal and does not
	correct bipolar violations.
Payload	Payload loopback is used to provide a loopback toward
	the network. The data portion of the DS0 is looped
	back.
Local	Local loopback will loop back the data from the
	customer side of both the T1 Network Interface and the
	T1 Drop/Insert Interface.
	Please Note: Network direction loopbacks in most
	cases can be initiated by the Telco. The front panel Test
	indicator illuminates when the T-1 is in loopback.

CSMIM-T1 Hardware Installation Guide 4-7