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Timing Options
Internal Timing
With Internal Timing, illustrated in
source
(1)
for T1 data output from the transmit buffer
requirements of a Stratum 4, Level II clock, as defined in AT&T Technical Reference 62411. The
remote CSU/DSU uses this as its timing reference and loops it back to the local CSU/DSU. The
local CSU/DSU recovers the receive T1 clock from the network receive T1 data and uses it to clock
T1 data into the receive buffer (3). The CSU/DSU also translates
the channel transmit and receive clock signals on the appropriate interface leads for each channel.
Select Internal Timing when using the SC 553 CSU/DSU in a private network that does not provide
timing (e.g., a non-DACS based service).
Note
A.Configure only one CSU/DSU in your network for Internal Timing, and configure the others
for Slave Timing.
B.Select the appropriate timing option for the customer equipment: The CSU/DSU provides
transmit timing on the channel's Tx Clk lead.
Network Receive T1 Data
Timing
S1
Source
1
Network Send T1 Data
Figure D-2
D-4
Figure
SC553 CSU/DSU
3
Recovered
Receive
T1 Clock
2
Internal Timing
SpectraComm 553 Fractional T1 DSU
Installation and Operation Manual
Timing Option Descriptions
D-2, the SC 553 CSU/DSU provides the send timing
(2)
to the network. This clock satisfies the
(4)
the receive T1 clock to provide
Receive
Buffer
Clock
Translator
4
Transmit
(Send)
Buffer
CH. Receive Data
CH. Rcv Clk
CH. Send Data
CH. Tx Clk
076R155-000
Issue 7
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