This Aquatica Dual Strobe Assembly (Replacement) can be used on the D90 and other recent Aquatica housings for Nikon cameras. Included are 2 Nikonos Bulkheads (#18916) that allow you to attach a strobe with a Nikonos 5-pin sync cord. Also included is 1 Hot Shoe Assembly (#18919). This part plugs into a Nikon camera's hot shoe.
All of these parts get connected through the Switchboard Circuit (#18915). The Switchboard Circuit has four 2 position switches. When all the switches are in the upper position, all 5 contacts are active, allowing you to use a TTL converter, or housed TTL compatible strobe that is attached to the main bulkhead. When the switches are in the lower position (default), only 2 contacts are active. So the main connector will work in manual flash mode only. The secondary bulkhead is wired with only 2 contacts for manual strobe operation in order to avoid possible conflict with the camera's electronic circuit.
Dual Strobe Assembly for Aquatica Housings for Nikon Cameras (Replacement)