Comtech EF Data CDM-625, Инструкция по установке и эксплуатации

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CDM-625 Advanced Satellite Modem Revision 1
Front Panel Operation MN-0000036 (Ref MN/CDM625.IOM)
5.4.5 CONFIG: Clocks
Clocking: TxClock RxBuffer/Clock
Clock-Ext Freq-Ref Int-Ref-Adjust (
34
)
Select one of the parameters using the
◄ ►
arrow keys – the submenus branches available are
TxClock, RxBuffer/Clock, Clock-Ext, Freq-Ref,
and
Int-Ref-Adjust
– then press
ENTER
.
5.4.5.1 CONFIG: Clocks
Æ
Tx Clock
Transmit Clock = Internal(SCT)
(Int(SCT),TxTerr(TT),RxLoop, ETTSTRxS) (
v
)
Use the
▲ ▼
arrow keys to select from the choices shown in parentheses, then press
ENTER
.
Internal (SCT)
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 Tx interface type is Audio.
Tx-Terrestrial (TT)
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. This is the
required setting when the modem’s interface type is G.703.
Rx-Loop-timed
Will allow the modem’s internal clock to be phase locked to the Rx buffer
clock source. This output clock is Send Timing. Choosing Rx-Loop will
not automatically select Rx-Sat as the buffer clock source. This allows for
increased flexibility for modem clock selection. Normally the user will
select Rx-Sat but the other choices also are available.
Example:
The user has an available high stability 10 MHz clock source
but the end equipment will only accept a clock at the information data
rate. Selecting Tx Clock = Rx-Loop and Rx Buffer Clock as EXT-REF will
provide receive timing and send timing to the end equipment that is
sourced from the 10 MHz reference.
Ext-TT (ST = Rx Sat)
Only valid if: RS422, V.35, HSSI or LVDS, Tx and Rx data rates are
equal, no RS, and no framing.
In this mode, transmit timing is taken from the TT pins, but ST is active
and will give out a copy of the Rx Satellite Clock. This has been
implemented to permit a particular variation of Loop Timing.
See
Chapter 9. CLOCK MODES AND DROP AND INSERT (D&I)
for
more information.
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