P300H
P300 Series Modem Installation and Operating Handbook
Page 67
the Station Clock frequency). Similarly setting Tx Clocking =
Ψ ®»ºøÍ¿¬÷
(ie with
Rx Clocking =
Í¿¬»´´·¬»
) would slave the Tx Clock to the incoming satellite clock
(which is what most other modem manufacturers means by Tx=Rx). In all
cases if the clock selected by the Rx Clocking fails, then the backup receive
clocks (as defined in 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 =
Ψ
®»ºøãÍ¿¬÷
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
Í¿¬»´´·¬»
or
ͬ¿¬·±² Ý´±½µ
? Because, with Rx=
̨ Ý´±½µ ײ
it causes a clock loop as
Rx=Tx AND Tx=Rx, with Rx=
ײ¬»®²¿´
it is the same as selecting Tx=
ײ¬»®²¿´
,
ie the second Tx Clocking option, and with Rx=
ÜÝÛ Ý´±½µ
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
Í¿¬»´´·¬»
or
ͬ¿¬·±² Ý´±½µ
.
