STARPLUS STSe Key System, Installation Manual

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Expansion Board Installation 3-23
Chapter 3 - Installation
STARPLUS STSe - Installation Manual August 2005
ISDN and T1 Clocking
When combining PRIB and T1 cards in one KSU, specific settings are important for proper
clocking. The Phase Lock Loop circuitry within the MPB synchronizes the clocking from the
Central Office to the clocking of the KSU. Popping, crackling, dropped calls, and one-way
transmission are usually attributed to the clocking not being synchronized correctly.
Example - Settings
The following example clarifies the clocking for these cards:
(1) T1IB and (1) PRIB
If both cards in a phone switch are connected to a telephone company clock (not
point-to-point T1), place the T1 clock switch in the enable position (UP) to allow it to receive
clocking from the telephone company directly.
Set the PRIB clock switch in the disable position (OFF), which allows the PRIB to synchronize
its timing off of the backplane (from the T1 clocking). If the T1 is a point-to-point T1, set the
PRIB in the enable position (ON), the T1 in the disable position (OFF).
When the switch is in the “up” position, it should be considered “ON”. When the
switch is in the “down” position, it should be considered “OFF”.