Aviation Electronics Technician 1 - Historic Naval Ships Association

completes the processing of radar and IFF video foron-line/off-line display. It works in conjunction withthe radar interface unit (RIU). The converter controlroutes the on-line/off-line selection to the RIU. Thereare five controls on the converter, of which four areused for off-line operation.ON LINE/TEST SWITCH.— This push buttonis used to select on-line/off-line operation of the radarset. When the ON LINE section is illuminated, theRIU is slaved to the nonacoustic operator’s keyset. Inthis mode of operation, all the manual selections onthe RIU front panel are deactivated. The onlyexception to this is the power switch.If you press the push button switch, it willilluminate the TEST section of the switch. With thissection illuminated, the radar set is in the off-linemode of operation. This means the RIU will respondto inputs from the RIU front panel.RANGE SEL MILES SWITCH.— This switchenables the operator to select radar range duringoff-line operation. The operator has the option ofselecting either 8, 16, 32, 64, or 128 nautical miles.RANGE ENTER PUSH BUTTON.— This pushbutton enters the radar range, selected on the RANGESEL MILES switch, into the RIU logic circuits duringoff-line operation. The indicator push button willilluminate amber, when pressed, denoting entry intoRIU logic. The indicator will return to green whenreleased.RANGE RINGS PUSH BUTTON.— Rangerings are added to radar video during off-lineoperation when this push button is pressed. Theindicator will illuminate amber, denoting that therange rings are selected. If you press the push buttonagain, it will deselect the range rings and return theindicator to green. Two range marks are developedfor the 8 nautical mile range, four marks for the 16and 32 nautical mile range, and eight marks for the 64and 128 nautical mile range.STORAGE TIME SECONDS SWITCH.— Thisswitch is not used at this time.MX-7974/ASA-69 Radar Interface UnitThe function of the radar interface unit (RIU) is toprovide radar data interface and the commanddecoding interface. Figure 3-7 shows the controlpanel located on the RIU. The RIU combines rawradar video from the APS-115 and IFF video from theIFF synchronizer. This video is then amplified androuted to the nonacoustic operator’s display.There are nine operating controls on the controlpanel of the RIU, of which three are not used. Thesethree are the OFFSET switch, the STOR switch, andthe OFFSET X/Y switch. Of the other six, five aredeactivated during on-line operation. Only thePOWER switch is activated.POWER SWITCH.— With this switch in theON-NORMAL position, operating power is applied tothe RIU. In the OFF position, there is no operatingpower applied.ENTER PUSH BUTTON.— This switch enablesthe operator to enter commands selected on the frontswitch panel into the RIU logic circuits. It must bepressed after each selection.HV ON/OFF SWITCH.— This switch enableshigh voltage to be turned on or off in the off-linemode. The HV ON/OFF position of the COMMANDSELECTION switch must be selected prior tochanging the position of this switch.COMMAND SELECTION SWITCH.— Thisrotary switch enables the operator to select the variouscommands for entry into the RIU logic circuits. TheFigure 3-7.-MX-7974/ASA-69 radar interface unit control panel.3-7