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Comm Systems
7-22-02
A diver just sent an email asking: "I need an opinion on FFM
comm systems.
I initially thought to go with a hard wired
rope system, due to needing a
rope anyway on search patterns, then thought maybe a wireless would be better,
because in a pinch, we could use any rope?"
I know this has been addressed in the past, but we have plenty of new
group members, so here is our answer to the question.
That is a question many teams face. We recommend hardwire comms for teams
who dive tethered. Wireless comms can be a real annoyance sometimes. OTS
makes the best comm. systems out there and even with their wireless comms
we find more problems than with their hardwire. When wireless comms work they
are great, but they are more of a headache more often.
Hardwire if taken care of properly, and if it is an OTS system, will
almost never fail. It takes seconds to set up. It is not another thing to worry
about because it becomes the tether line, and all the tender does it
connect the batteries, don the headset and turn on the box clipped to her belt or
backpack.
Wireless uses a surface station. Tenders need to be very mobile. One minute they may be
walking their diver through thick brush, they may be belaying their diver down a steep
embankment and then are themselves belayed by someone else, they may have to work on a
small boat, or they may need to be lying on their stomach on thin ice.
How can you do all that with a surface station? How do you perform a
dock walk
(box search, pier walk) with a surface station? You literally need someone
walking with the tender to hold the surface station box.
What are the advantages to a surface station? Yes you can plug in more
divers, but why would you want to do that? Each diver and tender are a
pair. We don't have tenders in charge of more than one diver. That is typically
less efficient and not as safe for low/zero visibility operations. We
don't want the speaker box used to allow anyone near the box to hear the diver.
The communication between the diver and tender is kept between the diver
and the tender so the diver has the confidence and trust that he or she can
say anything to the tender, such as "I'm a little spooked,. I didn't
thoroughly search a barrel I found on the last half of the last sweep because it gave
me the heebeejeebies, I want to do that over." The tender can relay to
the dive coordinator anything that the dive coordinator needs to hear. We
don't ever want two people talking to a diver at the same time.
If you want two divers to talk to each other
than can be done with
hardwire
so wireless is not necessary for that.
In regards to grabbing any rope in a pinch - it will take longer to set up
the wireless comm than it will to setup and use the hardwire, so saving
time/effort is not an advantage of wireless.
Push to talk is typically more common with wireless systems. That is not
the greatest. We prefer VOX. No need to push, just talk. Keep both hands free
for searching, saving yourself, or saving the primary diver.
So we recommend a simple,
easy to use, very dependable, very mobile, VOX (voice
activated), hardwire comm with a simple tender headset and MK7
or the newer version.
Andrea Zaferes
Lifeguard Systems & RIPTIDE
7-23-02
I understand your statements on wireless and hardwired diving..
My team is budgeting for full face masks and have tried the Ocean Reef and the
AGA with wireless comms from OTS as well as a system that was voice activated
with this big head piece.
I thought the voice activated was nice but OTS even with the push button talk
seemed clearer communication. The hard wire system works well in a tethered
dive situation... but we on occasion have to perform rescue services for two
separate boat racing associations and there is no time to set up a tether
system as well as with boats still sinkin we do not want to risk
entanglement in a sinking craft...
During races the boats often overturn or eject personnel.... we most often
perform a surface rescue but have on occasion hard to tie a marker to the
boat as it goes down. and then follow the line down with scuba to cut out
drivers and bring them to the surface...
No time for attaching systems Can't risk line entanglement… boats moving in
close proximity... Our boats act like blockers against race boats...
But most of the time we dive recovery following the lessons we have learned from
you and Butch and other teams doing this work...
Even tethered diving... I want to be able to talk to other divers especially the
safety diver so he understands what is going on before I get in trouble, when I
am in trouble, and while he gets me out of trouble.
We all have different scenarios where we must adapt to the situation
Shawn L. Connery
Dive Captain
Little Egg Harbor Twp. Fire Dist. #2 Dive Team
7-23-02
Just a bit of a clarification to Andrea's post. Great
information. There
are advantages and disadvantages to each system.
With hardwire you have full duplex communication. Not to be confused with
VOX. VOX is Voice Operated Transmission (X is an abrev. for
trans/mission-ceiver-mitter, i.e.: xceiver). With VOX your voice keys the
microphone. Not the best system when the fertilizer hits the fan. For you
firefighters or peace officers, imagine a distressed partner keying the mic
of his Motorola HT1000 and not letting off. This is what can happen when a
panicked diver goes audible, effectively shutting down communications for
all involved. VOX is only half duplex, meaning only one person can talk at
any given time.
PTT or Push To Talk is of course the same way (half duplex), however it
takes the deliberate act to talk. Most find PTT a better way to control
communications. However, with four wire (hardwire) system, the tender and
diver are able to talk at the same time just as on a telephone. The diver
can be monitored through out the dive. If he/she starts to stress, the
tender can hear the breathing rate, grunts, groans - everything. If the
diver starts to panic, the tender can shout him/her down. In a panic, a
diver may not remember to push to talk.
Another advantage is control. With the ComRope, the Tender not only has
bubbles, but can estimate distance, depth and direction along with the
constant communications. With a deployment, the Safety Diver knows where to
find the primary diver - at the end of the line.
The main disadvantage of a hardwire system is diving in a snag prone
environment. The wireless system will allow a diver to swim free through
pilings, trees and other hazards. This is something that has to be thought
through from a safety standpoint. Determine if this is a feasable method of
diving for your environment and teams level of training. Also take into
consideration the drag of the ComRope. There can be a lot of drag with a
150' piece of rope.
Through water communications systems are very reliable. Most of the
difficulties are in training. We find that the teams that use any, and this
goes for hardwire as well, of the systems regularly are more proficient in
their use and seem to have a lot less problems. The biggest problem is not
taking the time to learn how to effectively use the equipment.
Each type of system has its advantages and disadvantages. Examine the type
of diving you do, determine the best equipment and learn how to use it. As
with any discipline, you can have all the gear, but it gets down to the
training.
Dive safe...
John P. Hott
Ocean Technology Systems
7-24-02
John brings up some good points if you strictly operate in shallow,
fresh
water situations, areas with no obstructions or no overhead environments.
As a former hardhat diver I saw the advantages of hardwire but as a PSD I
have also seen many of the disadvantages, specifically when it comes to
searches conducted in the ocean where swells and depth can become a problem
when tethered.
As for the wireless OTS system, we have had ours for over seven years and
have yet to experience any problems with the system. We have really put it
through the "ringer" which included diving underneath a submerged freeway.
We were surprised that the wireless continued to operate even under these
conditions.
When it comes to dependability, the hardwire sounds like that best bet, but
when it comes to adaptability, the wireless tends to have its advantages.
Take Care,
Detective Estevan Martinez
Los Angeles County Sheriff's Department
7-25-02
Greetings all!
We use OTS Buddy Phones as our through the water
communications. There
were several factors that played in that decision. First, like was said in an
earlier post, each system (through the water or hardwire) has its advantages
and disadvantages. What matters is what works best for your Team! During our
Dive operations we may have from 1-6 or 8 Divers in the water at once
(depending on the mission). The ability for them to communicate, not only
with the surface but with each other, is paramount. The Safety Diver being
able to communicate with the Distressed Diver, both while in route to him and
once he arrives, is important to us. The Distressed Diver can give the Safety
Diver updated information about his situation or hazards the Safety Diver may
encounter on his way. The Safety Diver can have a calming effect on a
Distressed Diver, when talking to each other. Also if the Distressed Diver is
tangled or something of that nature by working (communicating) together they
can solve the problem. Should the 90% Diver have to get involved you have
three Divers plus the Tender who can all communicate with each other, to
solve a problem. We work from time to time with other Teams in our area, who
also use OTS Buddy phones. This gives us the ability to communicate with them
on joint operations. Expense was also an issue, we pretty much don't have a
"budget" so any gear we get is either donated by someone or purchased by the
individual Team Member.
We still train with our line pull signals. We review
them in our
pre-dive brief and each Tender reviews them again before his Diver gets in
the water.
Again, each system has its advantages and
disadvantages. Each Team may
have different requirements. Use what works for your Team!
Officer Ronny Phillips
Dive Master
Galveston (TX) Police Department
Marine/Dive Unit
7-30-02
Also on the Comm topic, John, thank you so much for that very
educational
posting on VOX, PTT, etc. Well done. I hope readers printed it out and put
it in their reference material. In your posting you bring up a good topic
for discussion. You wrote:
"The main disadvantage of a hardwire system is diving in a snag prone
environment. The wireless system will allow a diver to swim free through
pilings, trees and other hazards. This is something that has to be thought
through from a safety standpoint. Determine if this is a feasable method of
diving for your environment and teams level of training. Also take into
consideration the drag of the ComRope. There can be a lot of drag with a
150' piece of rope."
Our procedures say that if there are enough snags for a line to become
tangled in then the last thing a diver wants to do is to dive without a
tether. That is said with many exclamation points. If there are lots of
snags then change the type of pattern to decrease the number of snags.
Remember everyone that if the line can become snagged so can the diver. If
there is low or no visibility then without direct line access to the tender,
there is not way to gaurantee that the backup or 90% ready diver can find
and then reach that diver in a timely manner. Descending on a diver's
bubbles in low/zero visibility is make believe - especially in moving
water - and even if that did work, then it still would not address the
situation of a diver no longer breathing. So, as John said, determine a
feasable method for you. Feasable means you have a practiced, proven
contingency plan - and if you are not fully sure you can get your diver out
if it goes bad, then do not do it.
The OTS comm line is a good diameter. Our max recommended distance out for
that line is 125 feet, with a possible 25 foot extension depending on
conditions and the backup divers. (remember, the backup divers should be
equal to or stronger than the primary diver). With a proper harness and good
procedures a line can be held taught without much effort up to 125 feet. It
takes a little more effort to keep a 150 foot line tight, but not really
much more. The key is for the diver to be at a 45 degree angle away from the
tender: put the diver perpendicular to the line, and then turn the diver 45
more degrees away from the tender. That is the only position that will work
to keep the line taut with little effort for any reasonable amount of time.
If you are perpendicular to the line or if you are holding a loop in the
line - how can the line be kept really taut? How do you move sideways to
keep the line taut? If there is slack between you and your handloop, you
wont have a taut line without lots of arm effort.
If you can't picture what we're talking about, do it on land first. Hook up
to the line with a tender holding the other end. Lay on the ground with your
body perpendicular to the line. In that position, you will have to move
sideways to move away from the tender. Hence you have to move sideways to
keep the line taut. You can't keep the line taut by kicking because in a
perpendicular position kicking will only move you forward, not against the
line. If you try to do it by pushing off the bottom with your hands then the
search is screwed up. Now lay on the ground and swing 45 degrees away from
your tender so that your tender is looking at your right or left shoulder
blade. See that you can swim against the line and progress forward
simultaneously with little effort - all from the legs keeping both your
hands free for searching.
This does require you to have a good harness though with a tether point at
the solar plexus. The harness tether point needs to stay in one place
regardless of how hard you pull in any position. Too many harnesses we see
allow the tether point to move even as far up as under the arm pit when a
good taut line is held. - hence some teams go for the hand loop in the line
to prevent that from happening, and hence there goes the taut line. Many
teams are saying, hey, we do have a taut line and we do have a hand loop. If
you are saying that I ask you is your line pre-marked every five feet and is
your backup tender drawing your diver's pattern while checking that if the
diver is supposed to be at 37 and 1/2 feet out on this sweep that the diver
really is at 37.5 feet out. If not, you may find that your diver is not
exactly where you think the diver is. If you are tying knots in the line
every ten feet, the likelihood of an accurate pattern is slim to none (aside
from creating other problems with the knots). If your line is pre-marked,
but only at 10 foot increments, the pattern could easily be off anywhere
from 6 inches to 3 feet on any one or more sweeps. Add up that inaccuracy
after 5 sweeps and Houston, we have a big search problem. Seriously, try it
out on the floor, and then in the water and see what happens before you say
that we're wrong. Try things hands on before making absolute opinions.
Chuck, you also brought up an interesting topic: being spooked, the
heebeejeebees that I mentioned in an earlier posting. You posted that you
shouldn't dive if you are spooked. True, you should not dive if you start
out spooked, but I ask the group, is there anyone here who can honestly say
that they have never been spooked even for a minute during a low
vis/blackwater diver - particularly when something bumps into you (like an
eel) that you can't see or you bump into something that you also can't see?
I believe that can happen to anyone, even with 20 years of diving
experience. If we are prepared for such occurences then we can manage them.
For me, if I denied them, or if I told my students that they should never
feel spooked ever, then I think we wont be as prepared for those feelings.
Yes, Chuck, training, training is the key. There is a big difference between
being spooked and feeling nervous because you do not feel comfortable about
making the dive. If the latter exists then do not dive or abort the dive. My
definition of spooked is an irrational feeling that has nothing to do with
the safety of the dive. Spooked is not knowing what is causing you to feel
creepy. Does that make sense? You know the back up and 90% are ready to aid
you should you need them. You know the back up tender is monitoring your
bubbles and integrating that with your SAC rate to make sure you have
plenty of air, you know the back up tender is drawing your every location on
the profile map. You know you have a full pony bottle and will be told to
surface before your main bottle reaches 1000 psi. You know you have 3
cutting tools in the golden triangle area that you have practiced with. Yet,
all of a sudden you feel a shiver.
Andrea Zaferes
Lifeguard Systems & RIPTIDE
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