HDSL T200 HTU-R, Span Powered, 60 mA Installation and Maintenance Practice
A-2
61247026L1-5A
Loopback Process Description
In general, the loopback process for the HDSL system elements is modeled on the corresponding
DS1 system process. Specifically, the HTU-C loopback is similar to an Intelligent Office
Repeater loopback and the HTU-R loopbacks are similar to an inline T1 Repeater loopback.
Each HDSL system element is independently described by the state diagram shown in
. The four states are disarmed, loop-up, armed, and loop-up/time-out disable.
Figure A-2. HDSL Element State Diagram
State transitions result from in-band and ESF Data Link sequences as well as timeout operations.
The sequences and timeout values are as follows:
• Arming Sequence (in-band and ESF)
• Activation Sequence
• Deactivation Sequence
• Disarming Sequence (in-band and ESF)
• Loop-up Timeout
• Arming Timeout
DEACTIVATION
ACTIVATION
LOOP-UP
TIMEOUT
DISARM
DISARMED
STATE
ARMED
STATE
LOOP-UP/TIMEOUT
STATE
LOOP-UP/NO TIMEOUT
STATE
LOOP-UP
TIMEOUT
DISABLE*
* The Loop-up Timeout Disable function is currently not supported.
ARMING
TIMEOUT
