Comtech EF Data CDM-600/600L - Manual (Page 95)

CDM-600/600L Open Network Satellite Modem Revision 3
Front Panel Operation MN/CDM600L.IOM
5–19
5.4.5 CONFIG: CLOCKS
CDM-600L:
CLOCKING: TX-CLOCK
RX-BUFFER/CLOCK EXTERNAL-BASEBAND-CLOCK
CDM-600:
CLOCKING: TX-CLOCK RX-BUFFER/CLOCK
EXT-BASEBAND-CLK EXT-FREQ-REF INT-REF
Select a submenu branch using the [ ←][→] arrow keys – TX-CLOCK, RX-BUFFER/CLOCK,
EXTERNAL-BASEBAND-CLOCK for the CDM-600L, or TX-CLOCK, RX-
BUFFER/CLOCK, EXT-BASEBAND-CLK, EXT-FREQ-REF, or INT-REF for the CDM-600 –
then press [ENT].
5.4.5.1 CONFIG: CLOCKS Æ TX-CLOCK
TRANSMIT CLOCK = INTERNAL(SCT)
(INT(SCT), TX-TERR(TT), RX-LOOP, EXT-CLK)
Use the [ ↑][↓] arrow keys to select from the choices shown in parentheses, then press [ENT].
INT(SCT) 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-TERR(TT) 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 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-CLK External Clock: Indicates that an unbalanced high-stability source is
expected at the J9 BNC connector, or a balanced version at the P3A
connector. The frequency must match that programmed in the
CONFIG: CLOCKS
Æ EXTERNAL BASEBAND CLOCK menu, and
must be equal to the Tx data rate.