Comtech EF Data CDM-750 - Manual (Page 107)

CDM-750 Advanced High-Speed Trunking Modem Revision 2
Front Panel Operation MN-CDM750
5–29
5.2.2.4 CONFIG: Clocks
Clocking: Freq-Ref Int-Ref-Adjust
()
Use the W X arrow keys to select Freq‐Ref or Int‐Ref‐Adjust, and then press ENTER.
5.2.2.4.1 (CONFIG) Clocking: Freq-Ref
Frequency Reference: Internal
(Internal(with O/P),1,2,5,10MHz)
( v)
Use the ST
arrow keys to select Internal, Internal+O/P, Ext 1MHz, Ext 2MHz, Ext 5MHz, or Ext
10MHz, and then press ENTER. Note the following:
• Selection of Internal mode frequency‐locks the modem to the high stability ±0.06 ppm
10 MHz internal oscillator.
• In the Internal+O/P (Internal with Output) mode, the 10 MHz internal reference is used
as an output on the rear panel J8 | Ext Ref BNC connector. This mode is useful when
you desire to use a single frequency reference for both the modem and another piece of
equipment in the system. When selecting this mode, a green LED adjacent to the
connector illuminates to alert the user that the connector, normally used as input, now
has an output signal present.
• Selection of the Ext 1 MHz, Ext 2 MHz, Ext 5 MHz, or Ext 10 MHz modes will frequency
lock the modem to an injected external reference on the rear panel J8 | Ext Ref BNC
connector.
5.2.2.4.2 (CONFIG) Clocking: Int-Ref-Adjust
Internal Hi-Stability 10MHz Reference
Fine Adjust: +048 (+/-999)
( 34v)
With the Internal 10 MHz Reference selected, very fine adjustment of the Internal 10 MHz
Reference is possible. The adjustment value is retained in EEPROM memory, and is therefore
not lost when the NVRAM is cleared.
First, use the W X arrow keys to select a digit to edit, and then use the ST arrow keys to
change that digit. Press ENTER when done.
Changes made to the adjustment value take effect immediately, not after the
ENTER key is pressed.