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Installation and Setup
Timing Options
Timing options determine the clock source for data the SC 553 DSU transmits at its network and
cascade interfaces, and for both transmit and receive channel data. The DSU supports four timing
modes:
•
Receive Timing, based on the incoming signal from the network
•
Internal Timing, provided by the oscillator incorporated in the DSU
•
External Timing, based on timing signals from the DTE
•
Station Timing, provided by an external 1.544 MHz station clock connected at the lower
connector in Zone 1 of the back panel
•
Cascade Timing, based on the incoming signal at the Cascade Port interface
Receive timing is the default Transmit Timing option for the DSU.
While the SC 553 DSU can occupy the same shelf as the components of a SpectraComm 5000
system and be controlled through an SCM card that is also controlling an SC 5000 system, the DSU
timing is completely independent from the shelf timing used by the SC 5000 system. The SC 553
DSU is not involved in the shelf timing arrangement employed by the SC 5000 system.
Dedicated Remote Wake-up Procedure
A master SC 553 DSU, installed in an SC 5000 shelf or a MultiPak enclosure together with an SCM
card, can establish a Diagnostic Communication Channel (DCC) to a remote SC 553 DSU.
The DCC enables you to perform terminal interface management of the remote DSU from the
master DSU site.
An SC 553 DSU that is installed in the same shelf or enclosure as an SCM card is always a
diagnostic master unit, and one that is not installed together with an SCM card is always a remote
unit. A DCC can be established between a master unit and a remote unit, but not between two master
units.
SC 553 DSUs can support three types of DCC:
•
Facilities Data Link (FDL) DCC uses the FDL channel that is provided as part of the ESF
framing scheme.
•
Embedded DCC uses overhead data bits that are available when the data channel operates at an
N x 56 kbps rate.
•
DCC DS0 adds a DS0 for the DCC to those that are used to convey channel data.
Once the DSUs are physically installed at both ends of the link, use the following procedure to
establish the selected type of DCC and "wake up" the far end DSU so that it operates as a dedicated
remote unit. The procedure identifies the tasks that you need to perform. Chapter 3, Operation ,
contains the instructions for performing the tasks.
1. Begin a terminal interface session with the master DSU, using either a VT100 terminal or a
computer running the Telnet protocol.
2. If the two DSUs are being installed as a local, wire-line connection, go to Network Config-
uration and set the master DSU's Network Tx Clock Source to Internal. Leave it set to Re-
ceive for a standard Telco network connection.
3. Configure the appropriate options from the following list:
2-8
Dedicated Remote Wake-up Procedure
SpectraComm 553 Fractional T1 DSU
Installation and Operation Manual
076R155-000
Issue 7
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