P300H
P300 Series Modem Installation and Operating Handbook
Page 129
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
-§²½ ½¸¿²²»´
and to use all
the available overhead not already in use by the ESC channel. This can
provide a channel of up to 4.4% of the main data rate.
If the `Custom Features` feature is available (standard on P300-TCM), then
the overhead may be user assigned between the
ESC
&
Aux
channels,
allowing the desired Async ESC rate to be achieved for distant end M&C
(but not massively exceeded), leaving any spare overhead to maximise the
Aux channel data rate for BER testing.
IDR
IDR mode is only available if the IDR Option is fitted (standard on P300-
IDR and above). The
ESC
channel is the 8kbps synchronous ESC channel
standard on IDR Services (which may also be used for Asynchronous ESC
data if the Async ESC feature is available).
The
Aux
channel may be selected to be either 32kbps (in place of one
32kbps ADPCM audio ESC channel) or 64kbps (in place of both audio
ESC's). This provides a very useful channel rate for BER testing !
Custom Framing
Custom Framing mode is only available if the `Custom Features` feature is
available (standard on P300-TCM). Custom framing is based on either IBS
or IDR formats and custom framing provides the following advantages:
Based on
IBS
: A variable overhead may be added allowing both ESC &
Aux channels to be scaled to virtually any rate. This is achieved by setting
the ESC channel to the required Async ESC Baud rate, and changing the
split of the allocation of the overhead between ESC & Aux channels. The
total overhead then scales to provide the required ESC Baud rate in
whatever part of the overhead you have assigned to it, with the rest of the
scaled overhead for the Aux channel.
Based on
IDR
: As well as the features described above in standard IDR, it
is possible to reduce the normal 96kbps overhead (two audio ESC's) to
64kbps (one audio ESC or 32kbps Aux data) or 32kbps (no audio ESC's &
no Aux data). It may also be configured to use 16kbps ADPCM instead of
32kbps, allowing the full IDR features (two audio ESC) to be
accommodated in 64kbps overhead.
More interestingly
using the normal
IDR overhead of 96kbps together with 16kbps ADPCM for the audio
ESC's,
it may provide all the normal IDR features, but with the second
32kbps audio slot free to configure as a 32kbps Aux channel for
continuous BER testing.
