Symmetricom SDU-2000, User Manual

Page: 40 / 470

Product Overview
System Components
40 SSU-2000 User’s Guide 12713020-002-2 Revision D – April 2004
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.