ADC H2TU-C-231 - Manual (Page 28)

Provisioning LTPH-UM-1109-01, Issue 1
20 January 9, 2002 H2TU-C-231 List 2
H2TU-C Equalization (EQL) Option. The equalizer shapes the DS1 output signal of the H2TU-C to conform
to a very specific pulse template when it arrives at the DSX-1 cross-connect point. The degree of pulse-shaping
required is a function of the distance between the H2TU-C’s equipment bay and the DSX-1 panel. Thus, the
equalizer has six discrete settings, in increments of 133 feet to cause the maximized separation of 655 feet.
Alarm Pattern (ALMP) Option. To improve HiGain HDSL2 compatibility with the switch-to-protect features
used in Digital Loop Carrier (DLC) feeder applications, the H2TU-C-231 List 2 has an Alarm Pattern (ALMP)
option that allows you to select either an AIS or LOS DS1 output payload for the following alarms:
• LOSW on any loop
• LOS DS1
Power Back Off (PBON and PBOC) Options. Power Back Off Network (PBON) and Power Back Off
Customer (PBOC) allow the HDSL2 circuit to support two transmit power templates: default (DEF), higher level,
and enhanced (ENH), lower level. These are defined in Section 6.1.4.2 of the ANSI T1E1.4 HDSL2 standard.
Each HDSL2 receiver detects the level it is receiving during the start-up, pre-activation sequence. It then compares
this level to the level it should be receiving according to the PBON and PBOC option settings (DEF or ENH). If
the received level is outside the template limits, the receiver sends a message to the upstream HDSL2 transmitter
requesting the proper level. These levels are adjusted only during the start-up routine or if the PBON or PBOC
option settings are changed during normal operation. Since the ENH template levels are up to 15 dBm below those
of the DEF template, the ENH setting can be used to reduce crosstalk levels into adjacent circuits. (For example,
if crosstalk noise is being induced by the H2TU-R, set the PBOC option to its lower (ENH) level setting.
Conversely, if the HDSL2 signal at the H2TU-R is being affected by crosstalk noise induced from adjacent pairs,
set the PBOC option to its higher (DEF) level setting.
Bipolar Violation Transparency (BPVT) Option. The H2TU-C-231 List 2 improves compatibility with
Digital Loop Carrier (DLC) feeder applications because of its ability to transmit DS1 BPV occurrences between
its DS1 interfaces. This feature is required to support protection switching in DLC applications. Each DLC
terminal must be able to monitor the integrity of its Receive DS1 payload and then switch to the protect line when
the integrity of the path drops below specific user selected limits. An essential requirement of this feature is the
need for each DLC terminal to detect BPVs in its DS1 input. Standard HDSL systems correct DS1 BPVs at the
input and therefore prevent them from being detected by the DLC terminals to which they are connected. The
H2TU-C-231 List 2 and its associated remote units remove this limitation and become BPV transparent by
detecting and counting input BPVs at each end and then by replicating them at the DS1 output port of the distant
end.
The BPV count is converted into BPVs at the distant end during the following second at a rate of 1 BPV every
128 DS1 bits up to a maximum of 12000 (BER=7.7 x 10
-3 ). This maximum rate is more than adequate since it
exceeds the maximum 10 -3 BER required by most DLC systems.
Changing these Power Back Off option settings on a live circuit causes the HDSL2 loop to
momentarily drop and then re-acquire synchronization. This setting can also affect the
operating margins.