P300H
P300 Modem Installation and Operating Handbook
Page 100
Actions: 1:Buffer auto centre
2:BER 3:AIS 4:Back’ Alarm
Change, User-Opt, Operation, Actions Menu
6.10.3 Change, User-Opt, Operation, ACTIONS Menu
BUFFER
AUTOCENTRE
This selects if the receive buffer is automatically centred when the Rx traffic
returns to OK from the fail state. This takes advantage of any outage, and
ensures the buffer is centred every time normal operation begins. This option can
be disabled, as for minor outages the errors or sync losses caused by centering
the buffer may be larger than those caused by the outage itself. Default:
ENABLED
BER ACTION
This option controls how a high BER indication is handled. INTELSAT specify that
when the BER exceeds 1 x 10 the following actions are required: the Rx prompt
-3
alarm should be raised, AIS should be forced, and the backward alarm sent. This
option can disable the forcing of AIS and the backward alarm to maintain the
traffic as best as possible. Note the Rx Prompt alarm is still raised even if this
option is set to
NO ACTION
to disable the AIS and Backward Alarm.
Default:
ACTION
AIS ACTION
This option is similar to BER action above, except it specifies how the modem is
to handle the detection of AIS (the Alarm Indication Signal, all ones). INTELSAT
specify the required actions as: the Prompt Traffic alarm should be raised, AIS
should be regenerated (to prevent multiple noisy links building up enough errors
to stop the all ones being detected), and the backward alarm should be sent. In
continuous modes this option allows all three actions to be disabled. In
Drop/Insert modes the Prompt Traffic alarm and the backward alarm are
disabled, but AIS is still regenerated if it is detected. Default:
ACTION
BACK'ALARM
This option is only displayed if the Insert mux is active and set for Channel
Associated Signalling (CAS). It controls the forcing of the `abcd` signalling bits
passed to the terrestrial port to certain values when an incoming backward alarm
is received. Default:
Normal
. The options are
Normal
A backward alarm is sent out of the insert mux to the terrestrial
network (INTELSAT IESS 309).
Sig AIS
The `abcd` signalling nibbles for the
inserted timeslots
are
forced to all ones.
b=1
The `b` bit of the `abcd` signalling nibbles for the
inserted
timeslots
are forced to a one (Eutelsat EESS 501, SMS).
ab=11
The `a` and `b` bits of the `abcd` signalling nibbles for the
inserted timeslots
are forced to a one.