completes the processing of radar and IFF video for
on-line/off-line display. It works in conjunction with
the radar interface unit (RIU). The converter control
routes the on-line/off-line selection to the RIU. There
are five controls on the converter, of which four are
used for off-line operation.
ON LINE/TEST SWITCH. This push button
is used to select on-line/off-line operation of the radar
set. When the ON LINE section is illuminated, the
RIU is slaved to the nonacoustic operators keyset. In
this mode of operation, all the manual selections on
the RIU front panel are deactivated. The only
exception to this is the power switch.
If you press the push button switch, it will
illuminate the TEST section of the switch. With this
section illuminated, the radar set is in the off-line
mode of operation. This means the RIU will respond
to inputs from the RIU front panel.
RANGE SEL MILES SWITCH. This switch
enables the operator to select radar range during
The operator has the option of
selecting either 8, 16, 32, 64, or 128 nautical miles.
RANGE ENTER PUSH BUTTON. This push
button enters the radar range, selected on the RANGE
SEL MILES switch, into the RIU logic circuits during
The indicator push button will
illuminate amber, when pressed, denoting entry into
RIU logic. The indicator will return to green when
RANGE RINGS PUSH BUTTON. Range
rings are added to radar video during off-line
operation when this push button is pressed. The
indicator will illuminate amber, denoting that the
range rings are selected. If you press the push button
again, it will deselect the range rings and return the
indicator to green. Two range marks are developed
for the 8 nautical mile range, four marks for the 16
and 32 nautical mile range, and eight marks for the 64
and 128 nautical mile range.
STORAGE TIME SECONDS SWITCH. This
switch is not used at this time.
MX-7974/ASA-69 Radar Interface Unit
The function of the radar interface unit (RIU) is to
provide radar data interface and the command
Figure 3-7 shows the control
panel located on the RIU. The RIU combines raw
radar video from the APS-115 and IFF video from the
IFF synchronizer. This video is then amplified and
routed to the nonacoustic operators display.
There are nine operating controls on the control
panel of the RIU, of which three are not used. These
three are the OFFSET switch, the STOR switch, and
the OFFSET X/Y switch. Of the other six, five are
deactivated during on-line operation. Only the
POWER switch is activated.
POWER SWITCH. With this switch in the
ON-NORMAL position, operating power is applied to
the RIU. In the OFF position, there is no operating
ENTER PUSH BUTTON. This switch enables
the operator to enter commands selected on the front
switch panel into the RIU logic circuits. It must be
pressed after each selection.
HV ON/OFF SWITCH. This switch enables
high voltage to be turned on or off in the off-line
mode. The HV ON/OFF position of the COMMAND
SELECTION switch must be selected prior to
changing the position of this switch.
COMMAND SELECTION SWITCH. This
rotary switch enables the operator to select the various
commands for entry into the RIU logic circuits. The
Figure 3-7.-MX-7974/ASA-69 radar interface unit control panel.