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6.2.1.5
CONFIG: Clocks
Clocking:
Clock-Ext
Use the ◄ ►arrow keys to select a parameter. Press ENTER.
6.2.1.5.1
Transmit Clock = Internal(SCT)
(Int(SCT),TxTerr(TT),RxLoop, ETTSTRxS) ()
Use the ▲▼ arrow keys to select from the options shown in parentheses. Press ENTER.
Note that:
Setting
Internal (SCT)
Tx-Terrestrial (TT)
Rx-Loop-timed
Ext-TT (ST = Rx Sat)
Front Panel Operation
TxClock
Freq-Ref
CONFIG: Clocks Tx Clock
This is the required setting when the Tx interface type is Audio. Indicates that the unit
will supply a clock to the DTE, which is derived from its internal high-stability source.
This is the required setting when the modem's interface type is G.703. Indicates that
the unit expects to receive a clock from the DTE, to which the unit can phase-lock its
internal circuits. If no clock is detected the modem will substitute its internal clock and
generate an alarm.
Allows the modem's internal clock to be phase locked to the Rx buffer clock source.
This output clock is Send Timing. Choosing Rx-Loop does not automatically select Rx-
Sat as the buffer clock source. This allows for increased flexibility for modem clock
selection. While you typically should select Rx-Sat, other selections are also available.
Example: You have an available high stability 10 MHz clock source, but the end
equipment only accepts a clock at the information data rate. Selecting Tx Clock = Rx-
Loop and Rx Buffer Clock = EXT-REF provides receive timing and send timing to the
end equipment that is sourced from the 10 MHz reference.
Only valid if: RS422 or V.35, Tx and Rx data rates are equal, and no framing. This
mode is available to permit a particular variation of Loop Timing. In this mode, transmit
timing is taken from the TT pins, but ST is active and gives out a copy of the Rx
Satellite Clock.
Appendix E. CLOCK MODES
CDM-425 Advanced Satellite Modem
Rx-Buffer/Clock
Int-Ref-Adjust ()
Function
DROP & INSERT (D&I).
AND
6–31
Revision 0
MN-CDM-425
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