Paradise P300 specifications Comstream Sequential Mode Software =V2.12

13 Inmarsat (ISDN Backup) (Software >=V2.14)

12 OQPSK Compatibility Mode (Software >=V2.12)

Refer to the OQPSK Primer on page 66 before reading this section.

ACU's are located at the ends of the ship with the antennas, use coax cable to connect the `blocked` signal from the ACU to the modem along the ships length (screen=ground, centre=`block`).

11Comstream Sequential Mode (Software >=V2.12)

This switches the Sequential encoder and decoder to be “Comstream compatible” at Rate ¾ (in

Rate ½ it is already compatible and this flag has no effect, plus there is no Rate on the CM701). Note that when interworking with Comstream equipment with Viterbi FEC: BPSKfrequires P300 Tx & Rx spectrum invert, QPSK is OK without . With Sequential FEC: BPSK requires P300 Rx spectrum invert and both Tx & Rx spectrum invert in QPSK.

When using Offset QPSK (OQPSK) modulation, the in phase and quadrature components of each symbol do not change together (as with QPSK), but instead one component is delayed by half a symbol compared to the other. In order to be in accordance with general industry practises Paradise Datacom has changed which of the two components is delayed with respect to the other between the earliest of the P400 series modems and ongoing P400/P300 production. If you experience difficulty interworking in OQPSK mode between equipments, switch on this mode at the transmit end of the link which fails.

This additional feature allows an external equipment to provide an ISDN backup of the satellite circuit should the link fail or degrade beyond user set Eb/No or BER parameters. The ISDN backup being initiated from one end of the link only (in response to a failure in either direction) by the Receiver Ready line of the interface card being dropped. Exact additions are:

A backward alarm is transmitted if the user Rx BER or Rx Eb/No pass the user set thresholds (normally these only activate the deferred alarm). This signals the remote end that the circuit has degraded beyond the user thresholds (although it is already mandatory to send a backward alarm in IBS/SMS when the user BER degrades below the fixed threshold of 1 x 10-3).

When the user Rx BER or Rx Eb/No pass the user set thresholds OR a backward alarm is received, the interface card Sig’ Valid Out line is deactivated (normally this line deactivates only in response to a prompt Rx alarm, eg carrier loss). This line can be used with certain ISDN equipment to initiate an ISDN call.

14-15 Used for internal Paradise testing of enhanced modes we are evaluating. Not suggested for customer selection.

P300H P300 Series Modem Installation and Operating Handbook Page 204