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Clock Controller Installation
553-2901-200
Standard 11.00
— ENYL loop: Enable yellow alarm processing for loop
— EREF: Enable automatic switchover of system clocks
— SSCK x: Obtain status of system clock x
— SWCK: Switch system clock between active and standby
— TRCK aaa: Set Clock Controller track where aaa can be PCK (the
primary DTI/PRI reference), SCLK (the secondary DTI/PRI reference),
or FRUN (free running)
Procedure 12
Installing the Clock Controller in the ST, STE, 21, 21E, RT, 51/ 51C, and
NT half group
Note: Refer to the tables in this section to be sure you are using the
correct vintage.
1
Set the ENL/DIS toggle switch to DIS (disable) on the new circuit card.
2
If replacing an existing card, do the following:
— Perform a status check on the clock with the SSCK command in
LD 60. The new controller should have the same status.
— Disable the old card using LD 60.
Note: ERR20 messages may be generated. These can usually be
ignored. However, excessive clock switching should be avoided,
especially when counters are near the maintenance or out-of-service
thresholds. Excessive switching could generate threshold-exceeded
messages or cause the PRI to be automatically disabled. Check the
counters in LD 60. If necessary, reset the counters using the RCNT
command.
— Set the old card's faceplate ENL/DIS switch to DIS.
— Disconnect cables from the old Clock Controller card and remove
the card from the shelf.
Note: The Clock Controller status display in this mode indicates NO
UART (no universal async receiver transmitter). Do not perform a
clock status check when receiving this code.
August 1996
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