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P300H P300 Series Modem Installation and Operating Handbook Page 126
Channel for BER Test: [ESC]
1:Main data 2=ESC 3=Aux
Test, Internal BERT, Channel Menu
6.16.5 Test, Int' BERT, OFF/CHANNEL Menu
The test may run through the Main, ESC or Aux channels.
MAIN This first generates an `are you sure` screen before substituting the PRBS in
place of the Tx main traffic channel and monitoring for errors on the Rx Main
traffic channel. Note that for Closed Network mode only (ie no overhead at all) the
BER Tester cannot currently inject a test pattern into the main traffic channel (a
warning is issued on the screen). It can however receive and monitor a test
pattern injected by equipment at the distant end of the link. On a link where it is
necessary to use the BER Tester, switch to Closed Net Plus ESC mode, and if not
using the ESC set it for the lowest possible Baud rate which will result in an
overhead of <0.5%.
ESC / AUX ESC & Aux are defined below for the different service types. If either ESC or Aux
are selected but the channel has not been defined, then the user is prompted to
define the channel (and must then re-select the channel from this screen).
Closed Network ESC & Aux channels are not available in Closed Network mode (as there is
no overhead in which to carry them).
Closed Net Plus ESC Closed Net Plus ESC mode is only available if the Async ESC feature is
available (standard on P300-IBS and above). The ESC channel Baud rate is
used to determine the overhead added to the main data, allowing the
minimum possible overhead to be added (ie the minimum bandwidth to be
used), to provide the Async ESC Baud rate required. When the ESC channel
is used for BER testing the Async ESC is disabled and whatever bandwidth
was assigned to the Async ESC channel is used synchronously for BER
testing. The data rate to the satellite (main data + overhead) remains
unchanged.
There is no Aux channel facility in Closed Net Plus ESC, as this mode is
specifically designed to minimise the satellite bandwidth used, and hence all
overhead is assigned to the ESC channel.
IBS/SMS IBS/SMS mode is only available if the IBS/SMS feature is available (standard
on P300-IBS and above). The ESC channel is the channel which is normally
used to carry asynchronous data from earth station to earth station (typically
used for distant end M&C). When selected as the BER test channel Async
ESC data is not passed and the channel is used synchronously for BER
testing. It is only possible to define an ESC channel in IBS/SMS mode for the
BER test to run through if the Async ESC feature is available (standard on
P300-IBS and above). The ESC channel may be configured to provide rates
up to 4.6% of the main data rate for BER testing.
The Aux channel may be configured to provide the mandatory INTELSAT
oversampled low rate ESC (yes `ESC` but on the Aux port of the modem).
When used by the BER Tester it is used synchronously and provides a test
channel of 0.2% the main data channel rate. If the IDR Option is fitted
(standard on P300-IDR and above) which provide a synchronous external
Aux port, then the Aux channel may be set for sync channel and to use all