ZyXEL Communications Multi-service Access Platform MSAP2000 - Manual (Page 100)

6. System Design
MSAP2000 Technical Manual V3.0 6-3
6.2. Clock Synchronization
COT Timing
The MSAP2000 provides two Building Integrated Timing Supply
System (BITS) clock interfaces to connect with BITS equipment for
acquiring high precision clock. The BITS interface supports 2Mbit/s
and 2MHz clock inputs. It has clock detection and switchover functions.
The clock output with 2MHz is also provided. And without BITS, COT
can also have Line timing or internal timing to meet the precision of
clock.
External Timing (BITS): ITU-T G.703 square waves (2048 KHz) of
Framed E1 signals.
Line Timing: Selects any synchronous QE1M E1 interface input signals
from the COT network side/end
Internal Timing: MPM internal clock. Its frequency accuracy is
20 ppm.
Clock Priority
MSAP2000 can select its synchronous time source via LCT or NMS.
When the main clock source fails, the System can switch to the
secondary clock source, based on previous setup priorities.
RT Timing
MSAP2000’s RT accepts the following two types of timing sources:
„ Line Timing: each RT automatically selects a synchronous signal
from any trunk interface/transmission link input signals from COT
whenever the link to RT has been established
„ Internal Timing: RT will run in MPM internal clock if transmission
links experiencing link failure. Its frequency accuracy is 32
ppm.
GSH-R Timing
MSAP2000’s GSH Module can connect to the subscriber end GSH-R
(G.SHDSL modem), to provide data leased line services. GSH-R
supports Loop Timing and Internal Timing.
„ Loop Timing: GSH-R selects a synchronous clock from the Loop’s
input signals.
„ Internal Timing: GSH-R internal clock. Its frequency accuracy is
32 ppm.
Output
Synchronization
The Jumper on the MPM’s circuit board in MSAP2000 can be used to
setup output synchronization for 2048 KHz square waves or 2Mb/s and
Framed all “1” E1 signals. The Clock output provides the timing source
for other equipment to be synchronized to the networking timing.