Digital Trunk Clocking - NEC SL1000 Features And Specifications Manual

ISSUE 1.0
Description
The SL1000 CPU has a built-in clock source for all digital trunk units. Digital trunk units are connected
via an internal PLO (Phase Locked Oscillator) to derive Primary Clock from the network in priority
order. If priority is set up incorrectly, or if two primary clocks are coming in, slips may occur causing
improper data synchronization. The Phase Locked Oscillator (PLO) equipped with the SL1000 CPU is
the timing source for all digital trunk units in the system. The PLO synchronizes the system and clocks
signals from another office. When the SL1000 is a clock receiver office, the PLO generates the clock
signal according to the source clock signals received from the source office within the network. The
source clock signals are extracted from digital trunk units and are supplied to the PLO.
The PLO synchronization source priorities are as follows:
1. 1PRIU-C1
2. 2BRIDB-C1
3. CPU
Conditions
• If multiple PRIs exist, the system chooses the first one that synchronized with the carrier.
• If there are multiple PRIs and the one being used for the source goes down, the system begins to
count forward in slot numbers looking for the next available PRI.
• If multiple BRIs exist and no 1PRIU-C1 exists, the SL1000 CPU chooses the first BRI that synchro-
nized with the carrier.
• If there is one 1PRIU-C1 and the one being used for the source goes down, the SL1000 CPU looks
to see if there are any BRIs installed in the system. If there are no BRIs, the SL1000 CPU becomes
the new synchronization source. The reason for this is when a 1PRIU-C1 is installed in the system.
Default Settings
None
System Availability
Terminals
None
Required Component(s)
CPU
2BRIDB-C1
- OR -
1PRIU-C1
Related Features
ISDN Compatibility
Features and Specifications Manual

Digital Trunk Clocking

SL1000
D
1-163