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responsibility for ensuring that the filter is installed in the selected sl )t, since an empty
slot will cause a dead receiver. The override mode blanks the display. In addition, over-
ride signals cannot be handed off to the operator, since the machine has no way of deciding
the difference between a sideband signal with virtual carrier offset or a CW signal with a .
BFO offset. The override mode is invoked
wp.~n
both detector and l:·andwidth are sent in
the same command with the = sign. Sending either without the equals stores = data but
removes the Receiver from the override mode and restores it to nomlal operation. The
Receiver will respond to the following override commands (in the format $NO=XI=Y
where N is the receiver number, X is the mode selection number, anc': Y is the filter slot
number):
Mode Selection. The desired mode is selected by sending one of the following commands:
0=1 Selects envelope detector
0=2 Selects continuous-wave detector
0=3 Selects frequency-modulation detector
0=4 Selects ISB operation
Note that these "0" commands differ from the normal "0" comma'lds and are unique to the
override mode.
Filter Selection. In the override mode the filters are selected accordng to the fIlter slot
number instead of the fIlter bandwidth. The command is 1= N
wh~
re N corresponds to
the fIlter slot number. For example, the command 1=3 will select tt e fIlter inserted ·in filter
slot FL-3.
.
EXAMPLE 11:
The command $990=2I=3CR would result in receiver 99 being set t) the override mode
using the CW detector and the filter installed in fIlter slot FL-3.
To exit the override mode, an "IN" command is sent where "N" is the desired bandwidth
in kHz (not the filter slot number), and the" = " sign is omitted.
NOTE
When the Receiver is in the override Mode, both the
MOOE LCO and the FREQUENCY LCO are blanked.
In addition, status command S 1 will be ignored by
the Receiver.
3-29
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