Communications:
This new DESCO Air Hat comes equipped with a new speaker cup which incorporates the binding posts for
standard two-wire communications, and a port for the installation of a Marsh marine style plug assembly. This
port comes plugged from the factory unless the Air Hat is ordered with the two or four wire communications
plug option. The customer can install the plug assembly at a later time with parts DESCO can provide.
Instructions for connection of a four-wire communications equipped Air Hat to customer’s umbilical.
If your new Air Hat was ordered with the Four Wire Communications Plug assembly, the helmet is shipped
without any wiring connections made to the speaker. This allows the customer to match the connections in the
Air Hat to the umbilical communications line. The customer should check which wires are paired to the
microphone and to the speaker on the umbilical communications line. The wire pair going to the speaker should
be shortened so they can reach the binding post ends without any strain on them. Use the ring terminals
provided and connect the wires to the binding posts. Make sure the insulators are installed on the terminals as a
short circuit could result if bare terminals contact the helmet or each other. The microphone wires can be cut to
length according to the placement of the microphone, which is determined according to the customer’s location
preference.
Instructions for installing the four-wire communications assembly as a retrofit.
Remove the port plug and clean and inspect the threads. Check the fit of the bulkhead fitting by inserting the
fitting as far as possible by hand. It should easily engage the threads and turn in about 1/3 of the way. Remove
the fitting and mix a small amount of fast set two-part epoxy. Apply the epoxy to the threads on the fitting and
insert into the port. Tighten the fitting to approximately 3/4 of the length of the threads. Allow the epoxy to set
per the manufacturers recommendations. Slip the compression nut and ferrules provided onto the plug pigtail.
The nut and ferrules should be placed so as to leave enough of the plug out to connect to the umbilical without
straining. Approximate the final location of the plug in relation to the bulkhead fitting and strip off the excess
cable sheathing, leaving enough to pass through the bulkhead fitting into the helmet. Insert the cable through
the bulkhead fitting. If the cable resists passing through apply soapy water or silicone spray to the cable. Also,
the sheathing of the cable can be worked towards the bare wire ends of the cable to reduce the diameter to aid in
installation. Tighten the compression nut. Follow the connection instructions above to complete the installation.
Bench test the installation before placing the Air Hat “in service”.
Mounting Blocks:
Two mounting blocks have been added to the snout of the Air Hat. They are supplied with a 3/8”-16 x ½” Brass
hex bolt and a rubber washer. These mounts are useful for light and camera placements. Mounting ancillary
items on the Air Hat will change the natural balance of the helmet and should be taken into account.
Welding Shield:
A Welding Shield accessory is available for the Air Hat from DESCO (Cat. No.61001W/S). It features a
standard 4 ½”x 5 ¼” square lens, and the frame covers the entire faceplate. It comes with 2 stainless steel
screws, which should be used in lieu of the brass window screws.
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