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P300H P300 Series Modem Installation and Operating Handbook Page 64
the Rx Clock section) also source the Tx Clock as it is slaved to the Rx clock
whatever the source.
Note the P300 provides as standard the facility for Asymmetric Loop Timing (a
$1000 option from some vendors). This means you can set Tx timing = Rx
ref(=Sat) even if the Tx and Rx rates are different and it will generate the Tx Clock
from the incoming satellite clock. This works for any combination of rates, it
does not require the Rx rate to be higher than the Tx, or the rates to be in any way
related.
Finally, and only for those with inquisitive minds, why does it state earlier “This
option is only of any practical use when the Rx Clocking is set to Satellite or
Station Clock” ? Because, with Rx=Tx Clock In it causes a clock loop as Rx=Tx
AND Tx=Rx, with Rx=Internal it is the same as selecting Tx=Internal, ie the
second Tx Clocking option, and with Rx=DCE Clock it does something entirely
different for a reason even the inquisitive would find tedious, and uses the Station
Clock again if there is one or the Internal 1PPM ref if not. So this option really is
only of any practical use when the Rx Clocking is set to Satellite or Station
Clock.