The photos below are from my Dacor scooter, I have had it to a depth of 208 fsw and plan to take it deeper.

This is what happens if you don't stow your scooter on a boat the correct way. Mine fell over on the trigger side and broke the screw tits off, there is no fixing it. I had to get a new top end. I replaced the top with an Apollo top end. $$$$ :-(

All the pieces to the trigger.
The trigger has a magnet on it which causes a reed switch to make contact inside the housing. This is how I mark my batteries, so I can be sure I don't put a uncharged one in it.
This is the reed switch inside the housing, there is no thru hull connections, the magnet causes the switch contact. I used a yellow paint marker to mark the pitch settings so they are easier to see underwater.
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You need to check the hub O-rings after each dive to make sure you do not have a leak! This is where I keep my chargers at , all together.
This is what happens when fishing line makes it to the seal. Here you can see that the seal spring has been broken.
 
There you can see the fishing line next to the hub.