1.  Release upon receipt of an acoustic signal by the process of electrolytic erosion of a loop of stainless steel wire.

2.  Slant range 1,000 to 3,000 feet and up depending on water conditions.  (Note:  Sound travel is extremely variable in water depending on many factors).

3.  Operating depth is 0 to 1500 feet (666 psi).

4.  Topside interrogator is set to the four digit identification number of the unit underwater by pressing the increase or decrease key while viewing the unit identification number on an LCD display.

6.  The release unit has an external LED that flashes once every 10 seconds to indicate that the unit is on and listening and that the micro computer is fully operational.  The system can be checked out in air to give assurance that all is operational just before deployment.

7.  The AR-50-AA acoustic release unit uses nine lithium 'AA' cells and has a battery life of ten months listening in the water plus 75 releases with erosion link LK-40 (40 lb max) or 25 releases with erosion link LK-80 (80 lb max).   Batteries are user accessible and replaceable by someone capable of soldering the two wires (red and black) to a replacement battery pack model BAT-50-AA-L91.  As a lower cost operational option the user can make battery packs out of alkaline AA cells by allowing for about one third the number of releases and one third the amount of listening time on one set of nine alkaline 'AA' cells. 

Pictures of the AR-50-AA acoustic release system including the ARI-50 command unit, AR-50-AA release unit, LK-40 erosion links, battery pack BAT-50-AA-L91, battery test load BTL-50-AA, . . .  

Click on picture to view it, use back arrow to return.  

Click on picture to view it, use back arrow to return.  

Click on picture to view it, use back arrow to return.

DEPLOYMENT PICTURE:  Click here for one deployment scheme provided by a user of the AR-50-AA system.

FIELD TESTS:  Click here for a report on the AR-50-AA range and operation.  (Go to page 8 of the original document  heading Methods: and heading Discussion:).  (Look for 'AR-50' and 'Sub Sea Sonics' in the text).  Note that this is a xxx.pdf file and may be slow to load. 

VIDEO OF AR-50-AA:  Click here to watch a video of the AR-50-AA release deployed using a sacrificial weight.  Video supplied by NAUTA (see NAUTA-RCS.IT).  (File size is 9.1 megabytes of type .wmv).

MODEL AR-50-AA RELEASE UNIT. This release unit is deployed underwater and contains the receiver plus a micro computer  and batteries and holds a release link with a screw-on retainer cap for link replacement.  It turns on automatically when it is placed in the ocean by means of water contact to the link and the coil contacts. It has a unique 4 digit identification number that has been assigned to it by the factory.  This identification number is entered into the topside acoustic release interrogator (ARI-50) when a command is sent.  When the release command is received the unit applies its full battery voltage to the link (pos) and the 'coil' (neg) for 15 minutes.  This causes the small loop of stainless steel to erode away effecting the release.  This release unit has a single green LED that flashes once per 10 seconds when the unit is on and listening.  There is a checkout command that can be sent to cause the unit to switch on the erosion voltage for only 10 seconds which is useful for checkout.  Size:  2.00 inch diameter by 23 inches long (see picture above with dimensions).

An extra feature of the AR-50-AA release unit is that it can be commanded to emit low power (10 milliwatt) acoustic pings.  Receiving these low power pings requires a special acoustic receiver and antenna not supplied with this system.  Most users will not have the necessary receiving system but for those who do this signal can be used for verifying that the unit is operational or for locating the unit by sending it a command to emit pings for one minute.  Another command 'release-with-ping' can be sent to cause the unit to ping for 15 minutes while the release erosion is in process.  (Note that the 10 miliwatt power of this reply pinging is so low that it requires a good antenna, a good receiver, and quiet water conditions to pick it up at 1000 foot range.)

MODEL LK-40 EROSION LINK. This erosion link is made from a loop of stainless steel wire encapsulated in a PVC plastic holder. The erosion link operates by the fast electrolytic erosion of the exposed stainless steel part of its loop thereby freeing any line passed through it. This occurs when a positive voltage is connected to it by the internal electronics. It is partially coated with a durable paint to restrict the intended erosion to two points at the base of the loop to speed the release and reduce battery consumption. The erosion link is replaced after each release.  An O-ring is used to keep salt water out of the link connection cavity. The model LK-40 is rated at 40 lb on-axis load and erodes in typically three minutes.  A heavier load model LK-80 is rated at 80 lb and erodes in typically six minutes.  The LK-80 uses about three times the battery energy as the LK-40 reducing the number of releases per battery change.  A fresh battery pack (BAT-50-AA-L91) will give typically 10 months of operation plus 75 releases with the LK-40 erosion link (typically 25 releases with the LK-80).  For a large margin of safety these numbers can be divided in half.   

MODEL ARI-50 INTERROGATOR.  The interrogator is used to send the acoustic signal to the release unit.  With it comes a transmitting transducer (TD-50) which is placed over the side of the boat and into the water.   First the unit identification of the release unit to be released is set using the increase and decrease keys and viewed on an LCD display.  Second the specific action desired is selected (e.g.  release w/ ping).  Third the command is transmitted.  The signal takes about 15 seconds to send.  When a release command is received by the underwater release unit (AR-50-AA),  the release unit starts the erosion process.  For an erosion link LK-40 this takes from 2 to 4 minutes depending upon the battery state and the water temperature (4 to 8 minutes for the LK-80).

Click here for Manual and Specifications (xxx.pdf format use back arrow to return).

Click here for a comparison of the AR-60 vs. the AR-50 systems (use back arrow to return).

Back to home page