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Timing Options
Internal Timing
With Internal Timing, illustrated in Figure C-2, the DeskTop T1 DSU
provides the send timing source (1) for T1 data output from the
transmit buffer (2) to the network. (This clock satisfies the
requirements of a Stratum 4, Level II clock, as defined in AT&T
Technical Reference 62411.) The remote DSU uses this as its timing
reference (3) and loops it back to the DeskTop T1 DSU (4). The
DeskTop T1 DSU recovers the receive T1 clock from the network
receive T1 data and uses it to clock T1 data into the receive buffer (5).
The DeskTop T1 DSU also translates (6) the receive T1 clock to
provide the channel transmit and receive clock signals on the
appropriate channel interface leads.
Select Internal Timing when using the DeskTop T1 DSU in a private
network that does not provide timing (e.g., a non-DACS based
service).
a. Configure only one DeskTop T1 DSU in your network for
Internal Timing, and configure the others for Receive
Timing.
NOTE
b. Select the appropriate timing option for the customer
equipment: The DeskTop T1 DSU provides transmit
timing on the DTE interface Tx Clk lead.
C-5
GDC 048R154-000
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