User's Manual

1.3.2.11.9 Station Control Logic
The station control logic is duplicated in both U1 and U3. The logic responds to local operator control
through the pushbutton switch inputs as well as remote control through the parallel interface. The local
operator can perform the following functions:
a. Specify which DME/TACAN transmitter is to be designated as main.
b. Turn either transmitter ON and connect it to the antenna.
c. Turn either transmitter ON and connect it to the load.
d. Turn either transmitter OFF.
e. Toggle the bypass state of either of the monitored signal sources (Integral, Standby).
f. Silence the aural alarm (until the next event causes it to sound).
g. Toggle the state of local control. When local control is set, input from the keypad is enabled.
The following functions can be performed by the RMS through the parallel interface:
a. Functions a-g listed above.
b. Enable or disable the alarm signals from either one of the monitors. When a monitor's alarm signals
are disabled, it is functionally equivalent to the monitor producing constant alarms.
c. Set the "AND/OR" state of the alarm logic when it combines the alarm signals from Monitor 1 with the
alarm signals from Monitor 2. When set to "AND", both monitors must provide an alarm from the
same source to cause the station to transfer. When set to "OR", Monitor 1 signaling an alarm or
Monitor 2 signaling an alarm will cause the station to transfer.
d. Set the "Maintenance Alert" state. This lights the corresponding LED on the panel and sounds the
aural alarm.
e. Set the "Remote Control Fault" state. This lights the corresponding LED on the panel and sounds the
aural alarm.
In the alarm logic circuitry, the alarms from Monitor 1 alarm status are displayed on the panel. Similarly,
the alarms from Monitor 2 alarm status are displayed on the panel. If a given monitor’s alarm signals are
disabled by the RMS, it is equivalent to all of that monitor's alarm signals being asserted. The state of the
AND/OR setting determines whether both or either of the Monitor 1 or Monitor 2 signals are required to
produce a transfer condition. If one of the two +48V power fail logic signals goes active, the alarm logic
will force an alarm condition for the monitor pair that is powered from the corresponding +48V supply. In
order to avoid shutting the DME/TACAN station down, the alarm logic is forced to the AND state. This
allows the other monitor to monitor the system.
The alarm signals from the monitors have already been given the appropriate transfer delay times within
the monitors. This results in an immediate transfer when the combinatorial requirements of the alarm
signals are met. When a transfer condition occurs, the present transmitter that is connected to the antenna
system is taken off the air. The other transmitter is connected to the antenna system, and turned on (if it is
not already on). If the transmitter, not designated as main connected to the antenna system when the
transfer condition occurs, the control logic will enter the shutdown state and both transmitters are turned
off. Once the control logic enters the shutdown state, no further transfer operations will take
place until a local operator or the RMS turns one of the transmitters on and specifies that it is connected to
the antenna system. The Station Control Logic controls which transmitter is connected to the antenna
system by the status of the +24V ANT outputs.