Sub Sea Sonics AR-50-AA User manual

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Underwater Acoustic Release System
Acoustic Release Model AR-50-AA
(underwater release unit)
Acoustic Release Interrogator Model ARI-50
(topside command unit)
Sub Sea Sonics, San Diego, CA
[phone] (www.subseasonics.com)
OVERVIEW:
This underwater acoustic release system permits the underwater release of such items
as an instrument package lifted by a float, a bungee that when released performs a
desired action, etc. The acoustic release interrogator (ARI-50) sends a command to the
underwater acoustic release (AR-50-AA). An additional feature includes a command to
make the release unit become a very low power pinger to acknowledge operation or
permit tracking (requires a special pinger tracking receiver and antenna not included
with this system).
Each underwater release has a specific four digit unit identification number assigned to
it by Sub Sea Sonics. To send an action command to the underwater release unit the
following three steps are performed. First, the four digit identification number is
selected using the interrogator keys while viewing it on an LCD display (two line by 16
character each line). Second, the specific action command is selected using the keys
and LCD display. Third, both are transmitted to the underwater release unit.
The interrogator comes with a transducer on a cable that is placed in the water for use.
The interrogator must be connected to a 12 VDC battery such as a gell cell or lead acid
battery adequate to supply 5 amps during transmit.

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DEPLOYMENT OF A RELEASE UNIT:
A. Installation of batteries inside a release unit:
1. OPEN UNIT. Remove the two ¼-20 x 5/8” button head screws from the end plug
(Use caution; see SAFETY WARNINGS herein). To aid in the removal of the end
plug use a tool such as a Phillips head screwdriver inserted into the non-
threaded clear through hole in the external part of the end plug. Use this
screwdriver as a handle to help work out the end plug. It helps to use your feet
on this handle and gently twist and pull on the body of the release unit.
2. CONNECT BATTERY PACK. Check or connect a new a 13.5 volt battery pack
such as the BAT-50-AA-L91. It must have the red wire connected to the units red
wire (positive) and the black wire connected to units black wire (negative). These
wires are soldered in attempt to avoid the possible failure from an intermittent
connector. After soldering be sure to insulate using shrink tubing, tape or some
reliable means.
3. SLIP THE BATTERY PACK INTO PLACE. Slip the battery pack into the
housing keeping the red and black connecting wires dressed to the side while the
battery pack is slipped into place. After the battery pack is in then coil and stuff
the remaining slack wire in after the battery pack is fully in place. Use the foam
rubber piece to further cushion the wires and battery pack.
4. PREPARE THE END PLUG. Prepare the end plug using O-rings that have been
inspected for nicks and cuts and rot. O-rings are rubber and can rot with time and
exposure and on occasion are bad when new. Slightly stretching them while
inspecting them can reveal defects. The two O-rings used are #215 EPDM
durometer 70. EPDM O-rings do not ‘rot’ like the more common Buna N O-rings
can. Put silicon grease into the O-ring grooves and add some to the housing
bore. Use a silicon grease that does not attack rubber such as Dow Corning #4
available at such places as McMaster-Carr. Install the O-rings and spread the
silicon grease over them.
5. REPLACE THE END PLUG. Replace the end plug. Replace the ¼-20 x 5/8"
button head screws being careful not to cross thread them. Do not over tighten
them as the end plug and housing is a PVC plastic and does not have the
strength of a metal.
B. Verify that the release unit is operating:
1. ACTIVATE AND CHECK FOR GREEN LED FLASHING. Connect a 270 ohm
one watt resistor as a load across the water contacts (the link and the coil) to
both turn the release unit on and provide a load for battery testing under load.
(Alternatively a wet rag or higher resistance resistor could be used if testing
under a load isn’t deemed needed at this stage.) The LED will flash the unit
identification code in binary (see elsewhere herein) for about 30 seconds and
then go into listening mode. In listening mode it will flash the LED every 11

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seconds +/- 30%. Verify this flash of about one per 10 seconds. (If a BTL-50-AA
battery test load is available then it may be installed in place of the erosion link.
It will both turn the unit on, provide the test load, and indicate when a release
command has been received by turning on its red LED.)
2. IN-AIR TEST. Tests in-air can be performed on the release unit using the
topside interrogator (ARI-50) with its transducer (TD-50) connected. Place the
transducer within a few inches of the top center of the release unit for testing in
air. Any of the commands can be checked.
3. BATTERY TEST UNDER LOAD IN-AIR. To check the battery voltage select the
commanded action Brief Erosion (on for 10 seconds) or Release w/ Ping (on for
15 minutes). Use the BTL-50-AA (battery test load) or if not available connect a
270 ohm 1 watt resistor connected between the link and the “coil” contact. The
red LED on the BTL-50-AA will indicate that release erosion would be occurring.
A voltmeter can be used between the link (positive) and "coil" (negative) to check
the release battery voltage under the 270 ohm load. On the BTL-50-AA the
stainless steel wire protruding near the red LED is the positive contact. Connect
the positive voltmeter lead here. The “coil” water contact is the negative contact.
Connect the negative voltmeter lead there. Send the selected command. A new
lithium cell battery pack (BAT-50-AA-L91) should measure > 13.4 volts. A lithium
battery pack at the middle of its life nominally measures 13.0 volts. A near
expired lithium pack nominally measures < 12.5 volts. [Note: Allowance here is
made for the 0.1 volt drop which occurs across the internal switch inside the
acoustic release AR-50-AA at 50 mA]. Each 5 minutes of a 270 ohm load will
use up about 0.2% of the battery life while in release mode. To prevent this drain
on the batteries and to save checkout time the unit can be taken out of release
mode by removing the load and waiting for up to 60 seconds for the unit to check
for continuity and if none shut itself off. After it is shut off any testing can be
continued by again turning it on by reconnecting the test load, waiting about 20
seconds for the unit to stop flashing its unit identification code, and then sending
the next test command.
4. REMOVE TEST CONNECTIONS. Remove the 270 ohm resistor or any other
item (wet rag, BTL-50-AA, etc.) used to activate the unit. When submerged the
salt water will turn on the unit by providing a conductive path between the link
and ‘coil’ water contacts (just like the 270 ohm resistor did above). (Information
note: A special internal circuit puts a tiny electric current through the link/coil
water contacts once every 10 seconds to see if the unit is still in the water. This
electric current is extremely small and will not cause noticeable erosion of the
link. When a 'release' command has been received, this 'Am-I-in-the-water' test
occurs every 60 seconds. This longer time is to prevent excessive interruption of
the erosion process during a normal underwater release.) So during 'release' up
to 60 seconds of wait with no connection are required to let the unit shut itself off.
C. Installing a new erosion release link:
1. INSPECT THE POSITIVE CONTACT. Remove the retainer cap and the expired

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erosion link. Inspect the positive contact on the top end of the release unit (near
the ½ inch PVC threads). This contact is made from stainless steel and must be
solid (not eaten away during a prior release due to the mistake of not having an
O-ring in place protecting the link contact from the erosion process). Verify that it
is solid by pressing on it with a screwdriver or knife or some other tool.
(Stainless steel exposed to electrical erosion can turn into a honeycomb structure
that looks solid at first glance but when stressed it collapses).
2. INSTALL A NEW LINK WITH O-RING USING RETAINER CAP. Obtain a new
erosion release link (LK-xx). Put it in place using the retainer cap and being
certain that the O-ring is placed between the threaded contact end of the release
and the spiral contact end of the link. Optionally use a very small amount of
silicon grease or silicon spray on the O-ring. The O-ring specifications are 11/16
OD, 7/16 ID 0-ring #205 EPDM 70. It must be durometer 70. (The more
common Buna N can be used but is subject to cracking in air). Tighten the
retainer cap only after being certain that the O-ring is in place. Failure to have
the O-ring in place will not prevent the next release but will likely result in severe
damage to the positive contact (the contact that the link makes contact to).
Damage to this contact may make the AR-50-AA release unit worthless for future
releases and may be irreparable. Tighten the retainer cap as tight as possible by
hand. It can be felt to ‘bottom out’ when tight. As the retainer cap is tightened
verify that the link becomes securely held in place (i.e. it must be secure to
insure that the contact it makes is reliable)
3. INSPECT LINK. Verify the presence of each of the exposed places at the base
of the upside down ‘U’ shaped release hoop(s). At these points the metal of the
hoop must be directly in contact with the salt water at the time of release. As an
extra precaution verify that the small metal erosion points are not covered with
any hard to see coating. A small knife blade can be used to scrape a part of it to
inspect it. Do not remove the erosion focusing paint. Verify that there will be no
extra metal in contact with the link hoop such as a metal hook. If extra metal
were to make electrical contact with the erosion release link metal then it would
become part of what would have to be eroded away. This would consume extra
battery current, damage this metal, and if it is large enough may even prevent
release.
D. Final deployment:
1. Note the release unit’s four digit unit identification number needed for sending it
commands.
2. Verify that an O-ring was put in place inside the link retainer cap and that the link
is tightly held in place by the retainer cap.
3. Attach the release unit in the specific deployment configuration. Prevent any
heavy sideways impact from hitting the top (erosion link) end as it is possible to
break this retainer cap end off.

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4. Verify that no metallic material is touching the link (e.g. a metal hook) as this
could radically extend the erosion time and even prevent a release.
5. Verify that the pull on the link will be steady in one direction as continual bending
of the link metal might eventually break it off.
6. Verify that the ships RADAR is off (not likely a problem, but a worthwhile
precaution with high powered RADAR).
7. Verify that the green LED starts flashing when a conductive path is created
between the link exposed metal points and the ‘coil’ water contact. A wet rag,
wet fingers touching each, a resistor, a shorting wire (but if used don’t keep a
shorting wire on it during release), etc. can be used to initiate 20 seconds of the
green LED flashing. (This both final checks unit operation and verifies that the
link is in contact with the main electronics.)
8. If it is possible to see the green LED underwater it will flash about once every ten
seconds indicating that it is working and listening for a command.
9. To prevent a premature release from a prior release command verify that it has
been at least 15 minutes since the last release command (through air or water)
was sent.

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OPERATION OF THE INTERROGATOR:
Hookup of the acoustic release interrogator (topside command unit):
Supply 12 VDC from a gel cell battery or equivalent (needs 12 VDC at 5 amps for
transmit, but only 10 mA when not transmitting). Connect the transducer to the
interrogator and place the transducer in the ocean or very near the release unit if testing
in air. If testing is done in air the transmitting transducer may have to be adjacent to the
release unit body about six inches down from the link. If poor results are observed then
try moving the transducer slightly. Maximum ranges of 3 inches to 3 feet in air are
typical.
Operation of the interrogator (general concepts):
When first connected to a battery the LCD display on the unit displays a banner with
company name, model name, model number, firmware version number, etc. To break
out of this banner and get to the main menu hold the STOP key. The LCD now shows
"MENU FOLLOWS: press N for next". From here the NEXT key can be pressed
repeatedly to cycle through all of the activities that can be performed from this topside
box. When advanced to one of interest press the ACCEPT key to accept it. Note that
the second one down "Select Action…(unit action)" when selected with the ACCEPT
key puts the unit into a sub menu. This sub menu is the only sub menu on the topside
box. It is used to select the action desired by the underwater release. Once in this sub
menu the NEXT key cycles through all possible actions (actions by the underwater
release unit). See "ACTION = xxxxxx" headings on page 8.
Vocabulary: 'Box activity' generally refers to what the topside box is commanded to do
(selected from the main menu). 'Action' generally refers to what the underwater release
will be commanded to do (selected from the sub menu).
Interrogator box keys descriptions:
NEXT (N): Advances to next item on main menu or sub menu.
ACCEPT (A): Accepts the item currently displayed. If in the main menu it starts the box
activity currently displayed. If in the "Select Action " sub menu it accepts the action for
future transmission.
STOP (S): Stops the current box activity permitting changing to a new one. Has no
effect on the underwater acoustic release.
RELEASE ( R ): Used only to verify that it is okay to proceed with transmitting the
release command. It will not by itself cause the box to send a release command.
INCREASE (I) and DECREASE (D): Used for selecting the ID four digit number.
Operation of the interrogator (most common sequence):
After battery connection advance to the main menu by holding the STOP key. The

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display will show "MENU FOLLOWS: press N for next".
1. Press the NEXT key once to get to the box activity "Select unit Id.. (release
number)". Press ACCEPT to permit entering the unit ID. This four digit ID
number identifies the unit which is to receive the command. Use the INCREASE
and DECREASE keys to select the desired unit ID. Use the ACCEPT key to
accept it as ready for transmission. The display flashes and then goes back to
the top of the main menu, "MENU FOLLOWS: press N for next".
2. Press the NEXT key twice to get to the sub menu for entering the action to be
sent to the underwater release unit. The LCD will show "Select Action…(unit
action)". Press ACCEPT. The box has now entered a sub menu (the only sub
menu in this interrogator box). By pressing the NEXT key repeatedly all of the
actions that the underwater release can perform are displayed. As NEXT is
repeatedly pressed the list loops back on itself. The only way to break out of the
sub menu and get back to the main menu is to display one action and press
ACCEPT. This accepts it as the action that will be sent to the underwater
release unit when transmission (next step) is performed. As an example pick
"Brief Erosion…" by pressing NEXT until "Brief Erosion…(10 sec erosion)" is
displayed and then press ACCEPT. [BEWARE: This example, when transmitted
in the next step, will cause the release unit (AR-50-AA) to apply the battery
voltage to the release link (LK-xx) for 10 seconds. In this 10 seconds some of
the link will erode away if unit is in salt water.]
3. Press the NEXT key three times to get to the box activity "Transmit once….
(send command)". When the ACCEPT key is pressed the box will transmit both
the ID and the action selected above to the underwater release unit. During this
transmission process the transducer must be connected and in water (unless
testing in air). The single red LED on the topside box illuminates only during the
actual acoustic transmissions. Transmission takes about 12 seconds.
Understanding the 'busy time' of the underwater release unit:
Whenever a command has been sent and received by a specific release unit this
release unit is busy carrying out the command until the command is completed and it
times out. During this busy time the release unit will not alter its action and will not be
listening for another command. Sending another command will not confuse it; but, this
too-soon command will be ignored. The busy times for each action are listed in the
next paragraph and in a table below. Be particularly aware of the relatively long 15
minutes busy times for the two release commands. Trying to send another command to
a unit that is busy could be confusing if one does not understand that the underwater
release is not listening. If the unit is busy for 15 minutes performing a release then
deployment in salt water before this 15 minutes is up will cause unwanted erosion of the
release link. In other words, after testing in water or air with one of the release
commands the unit is busy for the 15 minutes applying the release voltage to the link.
BESURE TO NOT DEPLOY IN SALT WATER UNTIL IT HAS BEEN GREATER THAN

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15 MINUTES SINCE THE LAST RELEASE COMMAND WAS SENT. An alternative to
waiting 15 minutes is to reset the unit by keeping the water switch contacts dry for 60
seconds or more.
Release unit time-out (busy) times:
The following time-outs are used to free the release unit for another command. Pinger
Action = 60 sec (one ping per sec). Fast Ping Check = 2 sec. Brief Erosion = 10 sec.
Release with ping = 15 min. Release without ping = 15 min.
Information about the other box activities:
The following box activities are selectable from the main menu and are generally not
needed.
"Transmit Loop . . automatic repeat": This transmits the command in the same way that
"Transmit once" does except it continuously repeats the transmission of the ID and the
action that the underwater release unit is to perform. If there were to be a problem
getting the command through due to signal travel problems then this box activity could
be used to save operator time. Use the STOP key to terminate this "Transmit Loop"
box activity.
"Suppression . . . . .Is now ON" or "Suppression . . . .Is now OFF": For all known
applications leave it ON (the default). When ON the box precedes each timed pulse
transmission with a 'suppression' transmission with energy in the lower inhibit channel
frequency band. This prevents any acoustic signals that are weaker than the box
transmitted signal from interfering with the box transmitted signal. In short it blocks out
any man or animal interference as long as this interference is not as strong as the box
'suppression' signal.
"Directions . . . summary": This displays a brief directions-for-use summary.
An example of sending the command "Release with Ping":
Supply 12 VDC to the interrogator. Connect the transducer. Hold S for main menu.
Press N once to get to Select Unit Id. Press A to be able to select the unit identification
number desired. Use the I or D keys to set the unit Identification number. Once set use
the A key to accept the one selected. The LCD display will flash the selected unit
identification number and return to the main menu. Use the N key twice to advance to
Select Action. Use the A key to accept the "select action" sub menu. Use the N key
repeatedly to get to ‘Release w/ Ping…unit busy 15min’. Use the A key to accept this
action. Display will flash the action accepted and return to the main menu. Use the N
key three times to advance to Transmit Once. Use the A key to accept and perform this
activity. Since releasing is a non-reversible activity you will be asked to verify that you
want to perform a release with the choice of S for stop or R for release. Press R. The

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unit will display TRANSMITTING…, etc. as the transmission of the 2.5 second steady
synchronization/wake-up pulse followed by seven 20 ms precisely timed pulses occurs.
The command will have been completed when the LCD displays END XMIT CYCLE.
All of the other command setups and transmissions are similar to this one.
A list of the 'actions' which can be sent to the underwater release unit
follows:
These are accessed by the sub menu "Select Action" described above.
Action = Pinger (AR-50-AA):
Sending this action command causes the release unit to behave like a pinger for 60
seconds after which it times out. While acting as a pinger it emits one 20 ms ping once
per second (1.00 sec +/- 2%). These pings can be picked up on a sensitive pinger
receiver if the sea is relatively quiet. If a sensitive pinger receiver with tracking antenna
is available the direction to the release unit can be obtained. Note that the AR-50-AA
acoustic release units internal pinger only puts out about 10 mW of power. Accordingly,
if there is too much ocean noise the pinging mode may not be able to be picked up. A
pinger receiver is not supplied with the ARI-50 / AR-50-AA system. Vemco makes
pinger receivers that have been used successfully to pickup the weak 10 mW signal
from the AR-50-AA.
STORAGE:
1. Keep a new or used or dummy erosion link installed on each release unit when
storing to protect the plastic threads and prevent accidental erosion of the positive
contact (the one the link spiral contact touches).
2. If it is desired to prevent battery drain then keep the unit off by washing any salt or
other conductive material off the area near the link and coil. Keep this area dry and
free of any salt or contaminant that might conduct current.
3. Store out of direct sunlight.
4. Store such that the top (erosion link) end is protected from any heavy sideways
impacts as it is possible to break this end off.
CAUTION - SAFETY WARNINGS
1. Remove the housing end plug with extreme caution in case the housing leaked
or otherwise built up pressure. In the remote chance that the housing has

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leaked, pressure on the removable piece will be apparent as the two ¼ - 20 x
5/8” bolts are removed. If pressure is apparent then the housing has leaked and
the battery pack has been destroyed. At this point, to relieve the pressure
safely, use common sense and point the end plug at a solid wall or the floor and
keep it very close to the wall or floor while removing the two bolts. Use a face
shield. If the reason for the pressure buildup can be found then the unit can
possibly be cleaned up and put back into service as the electronics are protected
by encapsulation.
2. Do not touch the transducer while transmitting otherwise the sustained 2.5
second part of the transmission may overheat body tissues or cause other harm.
MISCELLANEOUS INFORMATION:
BUBBLES OFF OF THE "COIL" WATER CONTACT:
The stainless steel coil at the link end is the negative contact for the erosion process.
During release erosion there will be bubbles coming off of it. A deposit can form on the
'coil' which can generally be left there but it is best to brush it off. It seems to rub or
brush off easily when still wet from retrieval from the ocean.
EROSION TIME VS. WATER TEMPERATURE:
Lab tests indicate that the time to release increases 80% as the water temperature is
lowered from 70 deg F (21 deg C) to 28 deg F (-2 deg C).
EROSION TIME VS. BATTERY VOLTAGE:
Lab tests indicate that the erosion time increases about 150% (2.5x) as the battery
voltage decreases from 13.5 volts to 7 volts.
ACCIDENTAL LINK COATING INHIBITING EROSION:
Neither oil nor silicon spray applied as thick as possible right on the link erosion points
inhibit erosion. Both seem to disappear even when very gently submerged into still
water. However, if the contacts are covered with a thick covering of grease this will
prevent erosion if the covering is 100%. Tests show that a 90% covering only doubles
the erosion time. Accordingly, some accidentally deposited grease is very unlikely to
cause a problem.
LINK CONTACT SMALL CAVITY LEAK:
Should the link cavity (where the O-ring resides) happen to leak this will not prevent a
release. The majority of the electric current will still flow to the intended erosion points.
However, should the cavity have leaked there might be erosion damage to the unit
contact. It is a worth while precaution to inspect this contact by pressing on it with a
screwdriver to verify it is solid (not damaged by crevice corrosion during a prior release).

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VERY LOW RELEASE BATTERIES:
If the release unit battery voltage drops below 5.5 VDC due to unintended weak
batteries, a special supervisory circuit resets the micro controller which shuts off any
present activity (such as Release w/ Ping) and the unit returns to listen mode. This is a
friendly failure as the unit will be immediately ready to try again. If this should happen
wait for the batteries to recoup a bit and try again. If trying again is selected consider
sending a less current using command such as the Brief Erosion command. If it is sent
with Transmit Loop it will turn the erosion on for 10 seconds once every other
transmission cycle (about 10 seconds out of every 25 seconds) thereby reducing the
average load on the batteries. But this is only a last resort and will not be necessary if
adequate batteries are used.
THEORY OF OPERATION:
RELEASE RECEIVER:
The release unit receiver utilizes a low noise first stage followed by a high pass filter, more amplification
followed by a phase locked loop detector.
RELEASE UNIT LISTENING MODE:
During normal deployment the release unit spends most of its time listening for an on-frequency signal.
To keep the total battery current low (less than 200 micro amps) the receiver is turned on only once every
1.15 seconds (+/- 30%) to listen for a signal in the center frequency band (FM). This only takes 20 ms and
If none is heard (usually the case) the receiver is shut off and the micro controller goes to sleep. This
cycle keeps repeating until a signal in the center frequency band is detected and lasts longer than 8 ms.
When this happens the receiver stays on and checks to see that the signal stays on longer than 80 % of
the time for the next full second. It then checks for the signal absent for at least 300 ms. It then changes
to pulse timing mode and times the six time periods formed by a total of seven 20 ms pulses. (A
suppression frequency is transmitted before each pulse to suppress any on frequency interference such
as echoes, biological interference, or man made signals. This combined with long times between pulses
prevents interference from echoes.) Each of these 6 times is converted into an octal digit for a total of 18
bits. The first 12 bits contain the unit identification number. The next 3 bits tell the action requested. The
last 3 bits are a parity check. As the times are received they are checked against the unit identification
number for that unit. If any one of them is wrong the unit immediately goes back to listening mode where
it will not respond to the additional 20 ms pulses left in the command being transmitted.
RELEASE UNIT RELEASE MODE:
When the release command is received, the micro controller switches on the release sub-circuit for the
duration of the release mode time (e.g. 15 min). During this time the full battery voltage is applied to the
‘link’ (+) relative to the ‘coil’ (-) water contacts. The current flow is approximately 200 mA for a LK-40 link
with its two 0.025 inch diameter by 0.1 inch long exposed points. A current limiting circuit limits the current
to approximately 700 mA. A short across the ‘link’ to "coil" will not damage the release unit but will drain
the batteries. If a heavy load or weak batteries cause the battery voltage to drop below 6 volts then a
friendly reset of the micro controller would occur and a new command would have to be sent to restart the
intended action.
NOTES REGARDING THE CHECKOUT OF AN AR-50-AA RELEASE UNIT:
Unit Identification Number: Each underwater release unit has a specific "unit identification number" or unit
Id assigned to it. This number is between 0 and 4094 in decimal and is assigned by the factory. It is 12

12
bits in binary. In the unlikely event that this number is lost it can be read from a release unit by turning it
on and observing the flashes on its outside LED. Single flashes indicate bit one and double flashes
indicate bit 0. There is a spacing of about 1.2 second between each single or double flash. To observe
this remove the unit from the water to turn it off. Wait for up to 13 sec for the unit to check to see if it is still
in water and if not to shut itself off. (If unit was in the process of releasing then the wait for the out-of-
water check requires up to 60 seconds). Next, with a helper at hand, make contact with a 100 ohm to
100,000 ohm resistor (or a wet rag) across the ‘link’ and ‘coil’ contacts until the unit starts flashing. Write
down the flash counts (ex. 11 11 11 1 11 1 11 11 11 1 11 1) flashes = 000101000101 binary. Convert
these to decimal (ex. 0325 decimal). This is the unit identification number which must be used with the
topside command unit (acoustic release interrogator) to effect any of the actions that the release unit will
perform. This number can more easily be obtained by reading the number marked or tagged on the
outside of the release unit if one is still there. Note that the unit Id goes with the electronics inside and
cannot be changed. Unit Identification Numbers are assigned by Sub Sea Sonics. This permanent
assignment eliminates the need for unit identification physical switches with their possibility of switch
contact failure. It also keeps the assignment of numbers under the control of Sub Sea Sonics and
reduces the chance of two users selecting the same unit identification in the same region of the ocean.
Listening Mode Of Release: When the release unit is turned on (submerged or a resistor or a wet rag or
equivalent placed across the ‘link’ and ‘coil’) it first sends out its binary unit id by flashing the outside LED
and then goes into its listening mode. In listening mode it wakes up from sleep every 1.15 second +/- 30%
and checks for any signal on frequency FM (35714 Hz +/- 3%). If it does not hear one it goes back to
sleep. This listening mode can be confirmed by observing the outside LED on release link end flash once
for every ten wake ups which is once every 11.5 sec +/- 30%.
Actions By Release: When a command is sent by the Acoustic Release Interrogator, the release will flash
the LED in response. First it will flash with very faint flashes every time a 3 bit symbol is received and
confirmed correct for that specific release unit. There are 6 of these symbols. Next it will flash with normal
brightness to indicate which command it received as per the following:
One flash every 1.00 sec (60 sec total) => Pinger Action (unit pings once per flash also).
20 very fast flashes (2 sec total) => Fast Pinger Check (unit pings once per flash also).
100 very fast flashes (10 sec total) => Brief Erosion Check (unit pings once per flash also).
No flashing occurs during Release w/o Ping (release without pinging). Release lasts 15 minutes.
One flash every 1.50 sec (for 15 minutes) => Release with Ping (unit pings once per flash also).
These actions can only be interrupted by turning the unit off. To turn the unit off it must be removed from
water or the test resistor across the water contacts (link and coil) must be removed. This must be followed
by waiting for the unit to check the these water contacts. This occurs every 11.5 sec +/- 30% for all but
the 15 minute release which requires 60 seconds between am-I-in-the-water checks. [The reason for
these long wait times till off is to reduce water contact erosion by stopping all current flow until specific
check times. These check times last about 0.5 seconds.] Interrupting the commanded actions by shutting
off the unit before the commanded action times out can save a lot of operator time in system checkout.