PairGain 150-1592-02, Руководство пользователя

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Appendix A: Additional Technical Information 150-402-102-01, Revision 01
54 July 27, 1998 HRU-402 List 2
is required since the relay is performing the network signal loopback
function. This simple metallic loopback state remains until a loopdown
command is issued or the default timer (if enabled) expires.
When the HRU is in its AIS/DIS SmartJack metallic loop back state, its T1
input LOS, Code and Frame monitoring circuits are connected to the network
signal which is being looped back to these circuits through the loopback relay.
The CPE input signal is no longer being monitored since its input circuit has
been opened and terminated into 100
Ω
. The FRM and LOC LOS LEDs
indicate the status of this signal from the network. The Code LED also
indicates the code (AMI or B8ZS) of this signal if the Code option is set to
AUTO. It indicates AMI or B8ZS if the Code option is set to either AMI or
B8ZS respectively.
All of the HRU loopbacks towards the network (NREM and SMJK) are
metallic/logic (AIS/ENA) or metallic only (AIS/DIS). The SMJK and NREM
loopbacks are identical. They differ only in how they are initiated. The SMJK
identifying label indicates that the loopback was initiated by the 3 in 5 in band
or by the FDL command. NREM is used to indicate that the metallic loopback
was initiated by other than the 3-in-5 or FDL command (3-in-7, 16-bit,
addressable, repeater commands or front panel push-button).
The HRU-402 List 2 front panel LBK button is used to initiate and terminate
HRU loopbacks. To initiate a loopback in the HRU, press the LBK button for
five seconds. Pressing this button terminates all HiGain loopbacks that may
be present before executing an NREM loopback in the HRU. A loopback state
in the HRU can be terminated by pressing the LB button.