Both the network and instrument modules will be constructed like the junction box used for the Hawaii-2
Observatory (H2O) installation on the abandoned HAW-2 analog submarine telephone cable
(see http://www.whoi.edu/science/GG/DSO/H2O/). Figure 3 is a cartoon depicting this ocean observatory. The junction
box is about 2x1x1 m in size and is constructed entirely of titanium and plastic for corrosion protection. It contains two pressure cases to house the system electronics. An oil-filled manifold is placed about 1 m off the seafloor and houses a set of wetmateable electrical connectors to which instruments may be attached. The H2O junction box is designed to be recoverable for servicing, and plugs into the telephone cable at a termination frame. For NEPTUNE, the instrument modules will be very similar to the H2O design. The network mode will be permanently attached to the spur cable, and hence will have an attached gimbal and cable termination box to house the necessary connections.