3com MSR 20-20 참조 매뉴얼

Use the undo ft1 alarm-threshold command to restore the defaults.

# Set the number of detection intervals to 300 for the pulse detection duration 
threshold.

<Sysname> system-view

[Sysname] interface serial 2/0

[Sysname-Serial2/0] ft1 alarm-threshold los pulse-detection 300 

ft1 sendloopcode { fdl-ansi-llb-down | fdl-ansi-llb-up | fdl-ansi-plb-down | 
fdl-ansi-plb-up | fdl-att-plb-down | fdl-att-plb-up | inband-llb-down | 
inband-llb-up }

T1-F interface view

fdl-ansi-llb-down: Sends ANSI-compliant LLB deactivation request code in the 
FDL to removes loopback.

fdl-ansi-llb-up: Sends ANSI-compliant line loopback (LLB) activation request code 
in the FDL to start remote loopback.

fdl-ansi-plb-down: Sends ANSI-compliant PLB deactivation request code in the 
FDL to remove loopback.

fdl-ansi-plb-up: Sends ANSI-compliant payload loopback (PLB) activation request 
code in the FDL to start remote loopback.

fdl-att-plb-down: Sends AT&T-complaint PLB deactivation request code in the 
FDL to remove loopback.

fdl-att-plb-up: Sends AT&T-complaint PLB activation request code in the FDL to 
start remote loopback.

inband-llb-down: Sends in-band LLB deactivation request code compliant with 
the ANSI or AT&T implementation to remove loopback.

inband-llb-up: Sends in-band line loopback (LLB) activation request code 
compliant with the ANSI or AT&T implementation to start remote loopback.

Use the ft1 sendloopcode command to send remote loopback control code.

By default, no remote loopback control code is sent.

You may configure loopback on the far-end T1-F interface by sending loopback 
request code.

In LLB mode, all 193 bits (one synchronization bit and 192 effective bandwidth 
bits) in a T1 PCM frame are looped back. In PLB mode, however, only 192 effective 
bandwidth bits are looped back.