After about 2 months of on-off patrolling on SHIII I got to 1944 with just over 30,000 renown, playing 85%... it sure as hell made the new toy worthwhile though

I read in the manual that the XXI had a "Niebelung sonar" that was capable of finding target info whilst completly submerged... whilst the XXI has many new shiny surfaces and clocks with completely pointless red patterns on them, i haven't managed to find any extra controls for the sonar? Could someone please enlighten me?
(This should be on the Wiki)