Timing Options
Timing Option Descriptions
076R155-000
SpectraComm 553 Fractional T1 DSU
D-5
Issue 7
Installation and Operation Manual
Channel Timing (External/DTE Timing)
With Channel Timing, illustrated in
, the customer equipment provides its own channel
transmit clock signal
(1)
on the appropriate interface lead. The SC 553 CSU/DSU translates
(2)
this
clock to provide the send timing source for T1 data output from the transmit buffer
(3)
to the
network. The remote CSU/DSU uses this as its timing reference
(4)
and loops it back to the local
CSU/DSU
(5)
. 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
(6)
. The CSU/DSU also translates
(7)
the receive
T1 clock to provide the receive clock signals for the channel, on the appropriate interface leads.
Select Channel Timing when using the SC 553 CSU/DSU in a private network with the customer
equipment on the channel supplying the clock.
Figure D-3
Channel Timing
Note
Select the appropriate timing option for the customer equipment: The SC 553 CSU/DSU expects
external timing on the channel's Ext Clk lead.
Receive
Buffer
Transmit
(Send)
Buffer
SC553 CSU/DSU
Network Receive T1 Data
Clock
Translator
CH. Receive Data
CH. Rcv Clk
CH. Receive Data
Network Send T1 Data
Recovered
Receive
T1 Clock
CH. Send Data
CH. Ext Clk
S1
Timing
Source
1
6
3
4
Clock
Translator
7
2
5
