What ASW sensor is indicated here?
 

What sensor does the full circle dotted line indicate around this escort (the small one between the hydrophone and ASDIC indicators)?

http://users.frii.com/strider/Map01.jpg

The possible hearing zone.

"Hearing zone"? Sorry Sir, but hearing zone of what sensor? The 180 degree arc in front I believe is ASDIC (active sonar), and the 270 degree arc, farther out, I believe is the hydrophones with it's missing area in the ship's baffles. Is there a sensor which is indicated by the full circle who's range is in between the above mentioned two? As I said..."I believe"...please correct me if I'm wrong on these.

As always...:salute:

Initial visual counterdetection zone. If you're on the surface inside this circle, they tend to gravitate toward you (I've found...).

edit: j/k

HMMmm...I thought the "visual" zone was the one you can just see at the left edge of the map in my screen shot?

Hydrophone (aka passive sonar) extends further than Sound ( ASDIC) extends further than visual.

That means within the outermost circle, they can hear you on hydrophone - if you're making noise and they're gonig slow enough). Within the middle circle, they can find you with ASDIC, with the exception of the blind areas astern). Within the inner circle, the lookouts can spot you relative to what weather conditions allow.