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LTPH-UM-1049-02, Issue 2 Provisioning
H2TU-C-319 List 4E January 9, 2002 23
SF RAI to SF RAI-CI Toward Network (RACI) Option. In general, the Remote Alarm Indication -
Customer Installation (RAI-CI) signal is a RAI signal which contains a signature indicating that an LOF or AIS
failure has occurred within the customer’s network.
RAI-CI is transmitted toward the network when these two conditions are simultaneously true at the point from
which RAI-CI is originated (at the H2TU-R, toward the network):
• RAI is received from the CI
• No LOF, LOS, or AIS failure is detected in the signal received from the network.
Since RAI-CI meets the definition of RAI, it may be detected and used exactly as an RAI.
For ESF, the RAI-CI signal is a repetitive pattern with a period of 1.08 seconds. RAI-CI is formed by sequentially
interleaving 0.99 seconds of the unscheduled message 00000000 11111111 (right-to-left), which represents RAI
in the DL, with 90 milliseconds of the message 00111110 11111111 (right-to-left) to flag the signal as RAI-CI.
For SF, the SF-RAI-CI signal is transmitted in-band by setting each of the 24 channel time slots to 1000 1011
(left-to-right). In addition to the criteria specified above, the generation of SF-RAI-CI has to be held for 1 second
to examine the DS0 channels for the presence of a frame with an all-zeroes pattern. If present, the generation of
SF-RAI-CI is suspended for the duration of the all-zeroes pattern.
In all SF environments, the H2TU-R automatically converts a CPE DS1 payload with an embedded RAI signal
into an RAI-CI pattern toward the network if the RACI option is enabled (default). Such a conversion affects the
payload as described above. Disable RACI to avoid this payload-affecting conversion.
ESF RAI to SF RAI Overwrite (ROVR) Option. If the ESF RAI to SF RAI Overwrite (ROVR) option is
enabled, it allows a network ESF RAI or ESF RAI-CI pattern to be converted into a CPE SF RAI or SF RAI-CI
pattern, and overwrites the payload bits with the specific alarm patterns.
If the ROVR option is disabled, it prevents conversion of a network ESF payload with an embedded RAI pattern
and preserves the integrity of the CPE payload as it was originally transmitted.
Power Back Off (PBOC and PBON) Option. Power Back Of Network (PBON) and Power Back Off
Customer (PBOC) allow the HDSL 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 PBO C 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.
H2TU-R DS1 Frame Conversion (CONV) Option. Frame format conversion is only applicable to the
remote H2TU-R, but selectable by the H2TU-C or H2TU-R. This option enables the network to be ESF, which is
The SF RAI to SF RAI-CI option is only applicable in an all SF framing environment. If SF to ESF
conversion is active (the CONV option is set to either ACON or FCON), the SF RAI is converted
into ESF RAI in the FDL, regardless of the RACI setting.
Changing these Power Back Off option settings on a live circuit causes the HDSL2 loop to
momentarily drop and then reacquire synchronization. This setting can also affect the operating
margins.