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Timing Options
T1 DSU derives a master clock. For this method, the DTE must be
the master source of timing.
•
With DTE Split Timing, the customer equipment connected to the
DSU provides its own transmit clock signal (like DTE Timing),
but the network provides the master clock for the rest of the
network (like Receive Timing).
All timing options that include split timing require each
timing source to be traceable to the same Stratum 1 clock.
NOTE
The data rate on the network port is 1.544 Mbps. On the DTE port,
however, the data rate may be from 56 Kbps to 1.536 Mbps (1.544
Mbps when using unframed mode). The DeskTop T1 DSU
compensates for the difference in data rates by translating the clock
frequency when passing it from one port to another.
Table C-1
Timing Option Reference
Timing Option
Receive Timing
Internal Timing
DTE Timing
DTE Split Timing
Receive Timing
With Receive Timing, illustrated in Figure C-1, the network (or a
device at the remote end) provides the timing source (1). The DeskTop
T1 DSU recovers the receive T1 clock from the network receive T1
data and uses it both to clock T1 data into the receive buffer (2) and to
provide the send timing source for T1 data output from the transmit
buffer (3) to the network. The DSU also translates (4) the receive T1
Master Clock Source
Net.
INT
DTE
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C-3
Ch. Trans.
Clock Source
Net.
DTE
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GDC 048R154-000
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