Hydrophone, sonar and radar questions.

[welshterrier]

Im having problems understanding how they work ingame. At certain times the options ingame are turned off and im not sure how to make them work or activate them;

Hydrophone: Normal sweep, follow nearest sound target contact.

Sonar: Estiate range to contact, precise range to contact

Radar: One sweep, continious sweep, turn on radar (cant figure out how to turn it on)

If there are reasons why these cant be used at certain times in the game could somone please tell me why?

Also are some of these unavailable on certain subs, until they have upgrades?

Thanks for any help!