TM  1-1520-240-10 4-1-4            NOTE The concentric circle is a reference mark only and is not a range marking. 4-1-3.  Controls and Function, Radar Signal Detect- ing Control. CONTROLS/ INDICATOR FUNCTION PWR Switch Two position switch. At ON, power is applied to set. Set is operational after 1-minute warmup. TEST Switch Switch is spring-loaded to off. When pressed, the self test function is enabled. CONTROLS/ INDICATOR FUNCTION MODE Switch Two position switch. Selects synthetic voice message for- mat. Mode 1 (up) selects normal message format. Mode 2 (down) selects terse (abbreviated) message for- mat. Mode 2 reduces audio distractions when operating in dense signal environ- ments. AUDIO When turned clockwise, the audio output of the set is in- creased. Figure  4-1-2.  Radar Signal Detecting Set Control 4-1-4.  Normal Operation — Radar Signal Detecting Set. This paragraph provides radar signal detecting set oper- ating procedures. CAUTION To prevent damage to the antenna detec- tors  (when  operating)  never  operate  the AN/APR-39A(V)1within 60 yards of ground based  radars  or  within  six  yards  of  air- borne radar antennas. Operating the sys- tem closer than these limits may damage the antenna detectors. Allow an extra mar- gin for new, unusual, or high-powered ra- dar transmitters. CAUTION Excessive   indicator   display   brightness may damage the CRT. Set indicator BRIL control for readable display. a. Starting. (1) PWR switch — ON. Allow 1 minute for war- mup  –  Check  for  synthetic  voice  message  “APR-39 POWER UP”. (2) BRIL control — adjust display of (+) symbol (3) MODE  switch  —  Select  MODE  1  (up)  for normal messages. Select MODE 2 (down) for terse (ab- breviated ) messages. b. Self-test check. NOTE SYSTEM SELF–TEST provides a four step test of system functions. A complete system self-test is initiated any time the test button is pressed. The complete system self test runs in less than 30 seconds. The following is a description of the system functions. (1) TEST - As follows: (a) MODE switch — Set position 1 (up) (b) TEST switch — Press. A  synthetic  voice  long  count  is  performed.  The  audio message “SELF-TEST, SET VOLUME 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12” will be heard on the ICS. A display of two numbers which represent the installed software revision on the indicator; one number (OFP-Op- erational  Flight  Program)  at  the  top  and  one  number (EID-Emitter   Identification   Data)   at   the   bottom   (fig.