Symmetricom SSU-2000 User Manual page 38

Chapter 1 Product Overview
System Components
Three communications ports including two serial port connections (Serial Port-A
and Serial Port-B) and one RJ-45 Ethernet connector (Ethernet 10-Base-T).
Another serial communication port is also available on the front of the
Communications module
DTE/DCE switch is a slide switch (S1) that allows the user to select either a DTE
or DCE serial port interface.
Reference inputs and clock outputs
Local and remote alarm contact closures, divided into three classes:
– CRITICAL Alarms – Indicates an immediate service-affecting condition that
requires immediate user intervention (such as loss of Communications
module, loss of input power to the shelf, etc.). When a critical alarm condition
is detected, the CRITICAL ALARM relay is activated (alarm condition) and
the CRITICAL ALARM LED on the front of the Communications module lights
red unless power was interrupted. In this case the unit no longer has power.
– MAJOR Alarms – Indicates a condition that may require immediate user
intervention. When a major alarm condition is detected, the major alarm
relay on the rear panel of the SSU-2000 is activated and the MAJOR
ALARM LED on the front of the Communications module lights red.
– MINOR Alarms – Indicates that the unit performance is degrading. The
minor relay is activated and the MINOR ALARM indicator lights.
Two local oscillator connections – Local OSC-A and Local OSC-B are normally
used as outputs to feed other equipment but can also be used as inputs when the
shelf is configured with plug-in modules as a monitor only.
Two antenna connectors – used to attach radio receiver antennas. The A
antenna connector (J6) connects to slot 1A3; the B antenna connector (J7)
connects to slot 1A5.
Interface connector for the optional SDU-2000 Synchronization Distribution Unit
(output signal expansion system). Up to four expansion shelf can be connected
in daisy-chain fashion to an SSU-2000 shelf. A termination plug must be installed
on this connector if not using the expansion shelf.
SDU Backup Clock (D-clock) that can be used in the expansion shelf in the event
of the loss of clock A or B. The shelf also has optional rack mounting ears for
mounting in 19 inch EIA, 23 inch EIA and AT&T, and ETSI racks and cabinets.
Main Shelf Power Distribution
The main shelf accepts redundant –48 VDC power inputs from external supplies
and makes these inputs available to the modules via the motherboard connectors
anytime the 5-Amp fuses are installed on the rear of the SSU-2000 main shelf.
An On/Off switch is not provided, preventing anyone from accidently shutting down
the system. To shut down the system, the two fuses (Power Supply A and Power
Supply B fuses) must be physically removed from the rear panel of the shelf (see
Figure 1-9). If only one fuse is removed, the system senses the loss of the power
input and switches to the second power input.
38 SSU-2000 User's Guide 12713020-002-2 Revision F.01 – January 2007