P300H
P300 Modem Installation and Operating Handbook
Page 62
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 =
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
.