P300H
P300 Series Modem Installation and Operating Handbook
Page 83
6.6.28 Custom IBS Overhead Allocation
Several of the above paths lead to the following screen where the available overhead can be allocated
between the Aux port (if set to
ͧ²½ ݸ¿²²»´
) and the ESC port (if set to
Ý«-¬±³
). This option is only
available of the `Custom Features` feature is available (standard P300-TCM).
This sophisticated facility allows the operator for example to:
On high rate links specify a
low proportion
of the overhead to be assigned to the ESC channel
(still enough to provide the require async Baud rate) but then allocate the remaining overhead to
the Aux port configured for a Sync Channel, allowing external access to the rest of the overhead
for example other data or BER testing (internal or external).
When using Custom, IBS, Min overhead, allocate the overhead between ESC & Aux ports. The
overhead will scale to provide the
set
ESC Baud rate
however much of the overhead is
assigned to it, and increase / reduce the
total overhead
as appropriate. The remainder of the
overhead can be allocated to the Aux channel, again for extra data of BER testing (internal or
external). This effectively allows the
sync channel rate to be varied
(by changing the ESC rate
& overhead ESC assignment, which the overhead then adjusts to provide).
The screens are as follows:
O/h use: 1=TS16=XXX 2=TS32b5&6=XXX (YES)
3=TS32b7&8=XXX 4=TS48=XXX More/Help
Change, Tx/Rx, ESC/Aux/BA Define (IBS) ESC/Aux Custom 1
O/h use: 1=TS0b1=XXX 2=TS32b1=XXX
3=TS32b3=XXX 4=TS32b4=XXX Back Help
Change, Tx/Rx, ESC/Aux/BA Define (IBS) ESC/Aux Custom 2
Each of the `XXX` fields can display the following uses for that part of the overhead, and be toggled
between the differen
ssing the appropriate numbered key:
t uses by pre
ed
ort
ÓÚÉ
In use for the TS32 Multi Frame Word.
TS1
n use, they
TS3
/32nds
overhead, and are normally spare again see note 1. This bit can only be
TS3
red). Spare if the Aux port is not set to INTELSAT mode
cted, and the backward alarm facility has been disabled. This bit can only
TS32 bit 4
is 1/32nd of the overhead and is normally used for the Satellite TS32 Multiframe but is spare
óóó
The overhead locations are unus
ÛÍÝ
Defined for use by the ESC p
ß«¨
Defined for use by Aux port
ignalling
ÝßÍ
In use for Channel Associated S
Þñß
In use for the Backward Alarm
6 and TS48
are both bytes of the overhead structure which are free when CAS is not i
are each equivalent to 8/32nd of the total overhead and can be allocated to ESC or Aux.
2 bits 5 and 6
(allocated together) and
bits 7 and 8
(allocated together) both correspond to 2
of the overhead. These are normally spare, see note 1, and can be allocated to ESC or Aux.
TS0 bit 1
is 1/32nd of the
allocated to the ESC.
2 bit 1
is 1/32nd of the overhead, and is the bit allocated by INTELSAT for the low rate oversampled
ESC (available on the Aux port if so configu
or Note 1, can be allocated to ESC or Aux.
TS32 bit 3
is 1/32nd of the overhead and is normally used for the backward alarm, but is spare if
Custom IBS mode is sele
be allocated to the ESC.