User's Manual
Download the BTS – continued
PRELIMINARY
SC 4812ETL BTS Optimization/ATP
08/15/2000
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Select CSM Clock Source
A CSM can have three different clock sources. The Select CSM Source
function can be used to select the clock source for each of the three
inputs. This function is only used if the clock source for a CSM needs to
be changed. The Clock Source function provides the following clock
source options.
S Local GPS
S Remote GPS
S HSO (only for source 2 & 3)
S LFR (only for source 2 & 3)
S 10 MHz (only for source 2 & 3)
S NONE (only for source 2 & 3)
Prerequisites
MGLI=INS_ACT (green), CSM= OOS_RAM (yellow) or INS_ACT
(green)
Table 3-15: Select CSM Clock Source
Step Action
1 Select the applicable CSM(s).
2 Click on the Device menu.
3 Click on the Clock Source menu item.
4 Click on the Select menu item. A clock source selection window is displayed.
5 Select the applicable clock source in the Clock Reference Source pick lists. Uncheck the related
check box if you do not want the displayed pick list item to be used.
6 Click on the OK button. A status report window is displayed showing the results of the selection
action.
7 Click on the OK button to close the status report window.
Enable CSMs
Each BTS CSM system features two CSM boards per site. In a typical
operation, the primary CSM locks its Digital Phase Locked Loop
(DPLL) circuits to GPS signals. These signals are generated by either an
on–board GPS module (RF–GPS) or a remote GPS receiver (R–GPS).
The GPS receiver interfaced to CSM 1 is used as the primary timing
reference and synchronizes the entire cellular system. CSM 2 provides
clock syncronization redundancy, but does not have a GPS receiver.
The BTS may be equipped with a LORAN–C Low Frequency Receiver
(LFR) High Stability Oscillator (HSO), or external 10 MHz Rubidium
source which the CSM can use as a secondary timing reference. In all
cases, the CSM monitors and determines what reference to use at a given
time.
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