User's Manual

MODEL 2130 MARKER BEACON
Rev. A April, 2005 2-13
This document contains proprietary information and such information may not be disclosed to others for any
purposes without written permission from SELEX Sistemi Integrati Inc.
2.3.3.1.6 Positive Alarm Register
This register receives the positive (high True) alarms from the two potential monitors within a system. Depending on the
configuration of the alarm voting and bypass logic, the Alarm Register will report an alarm to the transfer state machines if
reported by the enabled monitors.
2.3.3.1.7 Negative Alarm Register
This register receives the negative (low True) alarms from the two potential monitors within a system. Depending on the
configuration of the alarm voting and bypass logic, the Alarm Register will report an alarm to the transfer state machines if
reported by the enabled monitors.
2.3.3.1.8 20 Second Delay Counter
The 20 second delay counter is activated whenever the system initially powers up or a transmitter has been shut down
without transferring to a standby system to ensure that the system will not radiate any signal for a period of 20 seconds
following the shutdown.
2.3.3.1.9 LCU Transfer Control State Machine #1 and #2 and Discrete Controls
The heart of the LCU is the two redundant transfer control state machines. These are configured by the RMS; receive key
commands from the front panel or from the RMS, and process alarms reported by the monitors after being filtered by the
Positive and Negative Alarm Registers. Once configured for on air, the state machines will drive out the required signals
to enable the transmit on clocks (1_TX_ON_CLK, 2_TX_ON_CLK), enable the +12V power to the synthesizer VCO's
(1_12VCO, 2_12VCO), and select the required system to be placed on the antenna (1_+12ANT_SW, 2_+12ANT_SW).
With the redundant state machines, detection of an error assures that the system generating the error will be removed
from the air. The LCU transfers to the standby system if configured to do so either immediately for a Hot Standby system
or after a 20 second delay for a Cold Standby system. If further alarms are detected, the LCU transfer state machines will
shut the standby transmitter down and block any further transmission for a minimum of 20 seconds. Restarts are under
the control of the RMS.
The LCU transfer control state machines report status back to the RMS indicating the state of the state machines, and any
shutdowns that have occurred. The front panel LED's reflect the current state of the state machines.
2.3.3.1.10 LED Control
Status is fed back to a local operator via the LED's on the front panel of the LCU. These reflect the state of the
transmitters and the various alarms as reported by the monitors.
2.3.3.1.11 Audible Alarm
If an alarm as reported by the monitors is detected that is not bypassed, the audible alarm is generated. The audible alarm
can be reset by pressing the Alarm Silence button on the front panel. In local mode, the audible alarm is disabled.
2.3.3.2 Local Control Unit CCA (1A1A1) Detailed Theory of Operation
Refer to Figure 11-14. The LCU controls the sequencing of the main and standby Marker Beacon transmitters according
to alarm signals from the monitors. It displays the status of the station and accepts control input from a local operator.
The LCU also provides status to and accepts control information from the PMDT or RCSU through the RMS parallel
interface. The LCU circuit card consists primarily of two Field Programmable Gate Arrays (FPGA's), discrete control logic
and digital interface circuitry. It also contains light emitting diodes (LEDs).
2.3.3.2.1 Power Supply
The power for the LCU CCA comes from two separate sources of +12 VDC through Schottky rectifiers CR29 and CR30.
The rectifiers isolate the two +12 VDC sources from each other and allow either to supply power to the board. The +12
VDC is converted to +3.3 VDC by a DC to DC converter, PS1. The +3.3 VDC supplies power for all the circuitry in the
LCU.