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as of 08/08/14
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as of 08/08/14
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Historically standard communications in diving helmets has been a two wire round robin system. A telephone base unit is on the surface with a two wire cable running down to a receptacle on the helmet. The wires are attached to a speaker/microphone mounted inside the helmet. The telephone unit defaults to receiving communication from the diver to allow the tender to monitor. When the tender wishes to talk he has to depress a switch. "Round Robin" refers to the diver and tender taking turns to communicate.
Our older telephones also had "Diver to Diver" switches which permitted cross communications between two divers connected to the phone. This feature was desired to prevent idle chatter between divers while working, which would impede necessary communications. The tender had to operate the switch to flip between the divers. This feature was dropped in the latest version of the DESCO telephone.
Many current diving companies have gone to a four wire telephone system that allows the diver and tender to speak simultaneously. This has advantages and disadvantages. The four wire system allows the tender more freedom of movement as his headset doesn't require a "push to talk" switch. There is instantaneous communication between the diver and the surface (i.e. the diver can hear the surface at the same time they hear him.) so the diver is kept aware of conditions above. The downside is there is less control over communications as everyone can speak at the same time which might hinder clear information transfer.
DESCO Two Diver Telephone
These are sometimes referred to as "comm boxes" or "radios". DESCO sells one telephone. It is a two wire type capable of handling two divers.
Our current Telephone
2-Diver 8-Watt Telephone
Cat NO 59702
This is a powerful two-diver telephone, which delivers a full 8 watts of audio output. The telephone is equipped with a high quality University Sound loudspeaker for clear communications in noisy environments. Binding posts are provided for an external speaker, and jacks are provided for a headset. There is also a jack for a tape recorder. Separate volume controls for the diver and tender permit adjustment for optimum quality of communication. The telephone is powered by a 12-volt lantern battery, which comes with the telephone. A set of binding posts is provided for powering the telephone from an external source such as a 12-volt automobile battery. The telephone is housed in a handsome, highly finished, shock resistant wood case.
One of our customers reports that the supplied lantern battery lasted 60 hrs of normal use. He also noted there was no degradation of sound quality when he switched from a 150 foot umbilical to a 300 foot umbilical.
Shown connected to a Telex headset
Classic Style Helmet Connections
On old helmets from the very late 1800's and early 1900's the communication line was hard wired to the helmet speaker. The line would feed through a elbow with a packing gland and nut to make it watertight. This system made it very difficult to detach the line for storage or repair. As helmet designs were improved dedicated telephone elbows with jacks to accept a plug came into common use. This allowed the air and communication umbilical line to be portable. With the introduction of the U.S. Navy Mark V Helmet in 1916 the "Navy" plug became virtually a standard.
The elbow contained a jack to accept the plug and was fully watertight through a leather gasket inside the plug nut, a packing gland and nut inside the helmet. and the elbow was filled with bee's wax. The plug was fitted to a length (usually 100 feet) of four wire cable. the cable also has a steel weave embedded in the sheathing so it could also serve as a lifeline. The wires were paired so as to make a two wire configuration. The four wire cable allowed for potentially using a four wire system at some later time. Finding comm wire for the big Navy plug can be an expensive problem. Also it may not be the best option if a customer has several helmets and all are not "Navy" equipped. We offer a four wire pigtail adapter cap option for helmets with the Navy elbow.
The DESCO Commercial helmet had a smaller plug and jack system. It functioned in the identical way. Most DESCO commercial helmets were ordered with the Mark V communications system as contractors had umbilicals set up for it. The Browne Commercial Helmet has a combination air & communications block on the back. It is designed to use a two or four wire communications pigtail through a bulkhead fitting. We also make up custom installations using modified standard parts.
Commercial Comm elbow w/adapter cap Browne Commercial Block Modified mask air elbow w/bulkhead fitting
Modified elbow w/bulkhead fitting Small binding posts with mount made from Mark V welding shield block
DESCO Air Hat Connections
The Air Hat was originally issued with a side block to hold the binding posts at opposing angles. They passed through Nylon bushings and were held in place with jam nuts. The speaker terminals were connected between the jam nuts. In these helmets the speakers mounted to the inside of the snout on the left above the exhaust outlet. This location while very good for picking up the diver's voice also allowed excess air noise into the communications as the speaker was located in the direct path of the air flow.
In February of 2004 new Air Hats were outfitted with a side mounted cup behind the snout placing the speaker away from the air flow. It also is closer to the diver's ear. The new cup has a smaller version of the binding post. The cup also has provision for a bulkhead fitting to use a two or four wire Marsh Marine type pigtail.
Large & small Air Hat binding posts
Inside the helmet the speaker/microphone (aka transceiver) is mounted in a telephone cup. The cup allows the speaker mount to be set closer to the helmet shell so as to keep it away from the diver's head. The cup allows for almost one inch of extra clearance.
Mark V telephone cup
The Commercial Helmets use a different telephone cup than the Mark V Helmet. The commercial cup does not have the bump out for the wire. Lightweight DESCO helmets also use the Mark V system with the commercial cup. We also use a small telephone cup on custom helmets.
Commercial telephone cup Small telephone cup
DESCO Air Hat
The Air Hat originally had a 2" Mylar speaker mounted on the inside left of the snout over the exhaust outlet. The speaker was press fit into a plastic speaker cup and held in the ring with a retaining screw.
Air noise was a problem in trying to clearly communicate. In the mid-1990's we started installing 2 1/2" Mylar speakers to improve sound quality. A problem arose in that many old Air Hats had the speaker ring too close to the front of the helmet. A 2 1/2" speaker would hit the window. These helmets would either have to stick with the 2" speaker or have the ring relocated. If this issue was present on helmets we took in for rebuild the ring was moved automatically as part of the rebuild.
Old type speaker installation in the Air Hat.
Large (2 1/2") speaker, small (2")speaker, and speaker for side cup for DESCO Air Hats.
The side cup speaker on the latest Air Hat are mounted in the cup using 3M™ VHB™ (very high bond) two sided foam tape. Other double sided foam tapes can be used to mount the speaker. We have found this 3M™ tape is the best available. This mounting system has two advantages, one quick and easy installation, and two the foam isolates the speaker from the helmet shell. A foam cover on the speaker further reduces air noise and keeps it from contacting the cup and causing a "buzz" while operating.