150-231-175-01, Revision 01
Maintenance
HLU-231 List 7E
September 23, 1998
21
To change any option:
1
Enter its character key, which is shown inside the parenthesis within each parameter description. This causes
the screen to refresh with the new settings.
2
After all parameters have been selected, press
to exit, then
to confirm. The newly selected parameters
are now activated.
DS0 Blocking Option
To set the DS0 Blocking option from the Main screen:
1
Press to select the Systems Settings screen (see
2
Press
for the DS0 blocking selection. The DS0 channels are blocked or unblocked by entering each channel
number. Multiple channels can be selected by inserting a space between each entry.
3
After all the new settings have been made, press
for (Exit) then
to (Confirm). The new choices are now
installed.
If DS0 blocking is invoked in a HiGain system that has an earlier version HRU that does not support the blocking
option, blocking only occurs at the DSX-1 output of the HLU-231. The HRU DS1 output will not be blocked.
Also, all blocked channels are temporarily unblocked for all HiGain system loopback tests for all DS1 blocking
settings. This allows the standard full bandwidth T1 loopback tests to be performed for all DS0 blocking settings.
If a customer of a fractional T1 service fills any of the unused DS0 channels with information other than an idle
code of all ones, the HiGain system blocks this information from reaching the remote end of the circuit and
replaces those DS0 channels with an all ones idle code.
The result of blocking the idle code is that the CRC checksum delivered to the remote end (when the payload is
in the BSF format) will not match the checksum calculated by the remote T1 CSU. This implies errors are being
made on the loop when actually the blocking function created the CRC errors. Enabled DS0 channels pass
error-free.
In order to avoid this condition, fractional T1 customers should fill the unused time slots with an idle code. This
is a common capability on Fractional T1 CSU/DSU, D4 channel banks, and other CPE devices capable of
connecting to Fractional T1 service.
DS1 Line Code Option
The DS1 line code option should always be set to conform to the type of DS1 service, AMI or B8ZS, being
provided by the HiGain system. The AUTO mode, which can adapt to either AMI or B8ZS, should only be used
in applications that require it (such as when HiGain acts as a standby circuit to DS1 circuits whose line codes are
not known or may be both AMI and B8ZS) since it has the following two limitations. The AUTO mode will induce
one BPV in the DS1 bit stream whenever it switches from AMI to B8ZS. The AUTO mode allows each HiGain
end, HLU and HRU, to set its DS1 mode to the code it is receiving at its local DS1 input port. This makes each
unit’s code independent of the DS1 code being received at the distant DS1 input port. Thus if the line codes being
received by HiGain are different in each of the two DS1 directions, the HiGain DS1 output codes will not match
their respective DS1 input codes at the other end. This could cause the customer’s received data to be AMI instead
of B8ZS and thus violate the one’s density rules by having excessive zeroes.
