P300H
P300 Series Modem Installation and Operating Handbook
Page 65
If the Modem is in
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mode (low rate format) then it is possible to maintain the
Timeslot ID even with an IDR overhead structure. Refer to the section "Timeslot identity
maintenance" in Appendix F on page 214 if a refresh is required. Note that this is only offered
under Custom IDR to simplify normal IDR menu operation, but Custom IDR can be selected
with all the possible custom features set to `Normal` to allow normal IDR operation, but
with
timeslot ID maintenance
. Note that for low rate IDR carriers (<1544kbps) INTELSAT specify
the IBS overhead structure, but the Modem can operate the IDR 96kbps overhead (and use
Drop/Insert) even down to 64kbps.
If the Modem is in
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mode (low rate format) then the following prompt is displayed:
TS identity over satellite: [?]
1=Maintain 2=Don t care (Normal)
Change, Tx/Rx, Baseband, Drop/Insert, IDR Maint' Menu
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The dropped/inserted timeslots will be aligned in the satellite IDR frame in order
to maintain the timeslot identity.
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The dropped/inserted data will be arbitrarily placed in the satellite IDR frame
and the identity of the timeslots will not be maintained (as with normal IDR).
6.6.6
Change, Tx/Rx, Baseband, OTHER Menu
If the IDR option is fitted (standard on P300-IDR and above) then the modem can generate a 64kbps
carrier comprising just of two 32kbps ADPCM audio channels, or a 128kbps carrier comprising 64kbps
data (from the main data interface of the modem) plus two 32kbps ADPCM audio channels. These
modes are effectively an emulation of and are compatible with the popular P1348/P1448 voice/data mux
card used often in SNG applications. The choice between which mode is made on the following menu:
Voice/Data mux (P1348/P1448 emulation): [?]
1=Audio 2=Audio+64k Data
Change, Tx/Rx, Baseband, Other Menu
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A 64kbps data stream is generated from the two 32kbps ADPCM audio ports
normally used for the IDR Audio ESC function. Closed Net Plus ESC, IBS or
Custom IBS overhead is required in order to maintain the octet alignment (part
of timeslot ID maintenance) in order for this to function.
On the Tx path the clock mode is forced to internal, and on the Rx mode the
clock mode is forced to satellite (as the terrestrial interface is audio only there
are no clocking issues).
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A 128kbps data stream is generated, 64kbps from the two 32kbps ADPCM
audio ports normally used for the IDR Audio ESC function plus 64kbps from the
main data port. Closed Net Plus ESC, IBS or Custom IBS overhead is required
in order to maintain the timeslot ID and hence keep the channels separate in
order for this to function. Normal clocking selections are available.