Check out sys.txt, this entry should look like this:

[warning]
is_spoken=1
speedcam_enabled=1
speedcam_warning=1
speedcam_max_lookahead=3000
speedcam_maxdistance_from_road=10
speedlimit_warning_visual=1
speedcam_continuous_approach_beep_when_tonal=0
overspeed_sound=1
warn_distances="130:1000,90:690,70:690,50:690,30:540"
skin_speedcam_audio_path="speedcam_ru"