User's Manual

1.3.2.11.2 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.
1.3.2.11.3 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.
1.3.2.11.4 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.
1.3.2.11.5 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 +24V power to the synthesizer VCO's (1_24VCO, 2_24VCO), and select the
required system to be placed on the antenna (1_+24ANT_SW, 2_+24ANT_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 LEDs on the front panel reflect the current state of
the state machines.
1.3.2.11.6 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.
1.3.2.11.7 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.
1.3.2.11.8 Monitor Alarm Interface
In order to insure that a monitor alarm signal is communicated to the control logic, redundancy is
incorporated into the monitor alarm signals. Each alarm signal is sent as two signals, one active high and
the other active low. In the LCU, resistors are used to pull each of their signals to their active (alarm) state.
This insures that an alarm condition will be sensed if there is an open in either alarm line. If an alarm line
is shorted to its inactive (non-alarm) state, the other line will communicate an alarm condition. If the
1_INT_ALARM+ signal is disconnected, a resistor will pull the input high resulting in an alarm condition
being sent to the control logic in the EPLD U3. If the 1_INT_ALARM- signal is disconnected, a resistor
will pull the input to a low logic level.