Great discussions here. Ed, the only thing that I don't like about the electromagnet approach, and I had considered it before, is it is an additional load on the battery which I do not want to impose.
The DT is an "If all else fails" totaly independent approach to trying to find a boat on the bottom that has not responded to anything else for one reason or another.
I do plan on putting the DT in it's own WTC along with it's own battery. I plan on either keeping the servo in the DT WTC or possibly extending the servo leads outside of the WTC to a waterproofed servo. Haven't decide which yet though the former approach seems better. I also want to make sure that whatever system I implement it does NOT put a load on the DT battery until Timeout. I want to preserve the battery charge as much as possible. I would consider loading the battery at Timeout, which should be almost never and at that point who cares about the battery condition as long as it will support the Timeout event.
Robert, I see no problem with your approach other than the possible drain on the battery due to the electromagnet depending on how you implement it; always ON until DT Timeout (battery drain) or always OFF until DT Timeout.
Qualified in Submarines 1965
"D..n the pressure, Six-Zero feet!"
"Most men would rather die than think, Most of them do!" - Bertrand Russell
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