Acoustic Release Interrogator Model ARI-60

AR60MAN.doc or AR60MAN.htm revised 6-18-05:

Underwater Acoustic Release System

Acoustic Release Model AR-60-E (erosion) and AR-60-M (motor)

(underwater release units)

(topside command unit)

Sub Sea Sonics, San Diego, CA

(619) 286-7546 (www.subseasonics.com)

OVERVIEW:

This underwater acoustic release system permits the underwater release of an instrument package, a float, a rubber-cord tensioned line that when released performs a desired action, etc. The acoustic release interrogator sends the acoustic command to the underwater acoustic release. Additional features include commands to make the release unit become a pinger to acknowledge operation or permit tracking, a transponder to permit range display, and a battery report that tests the battery under load and reports its condition via a ping rate. Additional commands are available to use in system checkout.

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 this identification number is selected using the interrogator keys while viewing it on a two line by 16 character each line LCD display. 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 gel-cell or lead acid battery to supply 5 amps during transmit.

DEPLOYMENT OF A RELEASE UNIT:

A. Installation of batteries inside a release unit:

Remove the two ¼-20 button head screws on the sides of the unit which secure the end plug in place (Use caution; see SAFETY WARNINGS herein). (Note that the two 10-24 acorn cap nuts on the end are only the water contacts for unit activation and have nothing to do with battery access.) To aid in the removal of the end plug use a tool such as a Phillips head screwdriver inserted into the non-threaded 5/16 inch (0.312 inch) clear through hole in the center of the end plug. Use this screwdriver as a handle to help work out the end plug.

2. Check or Install an 18 volt battery pack such as the BH-60L (normally supplied). It must have the red wire to positive and black wire to negative. With the BH-60L battery holder it must have all 12 cells installed with the correct orientation. (Inadvertent backward installation of one or more cells will result in rapid discharge of those cells through an adjacent diode and resistor causing the diode and resistor to get hot. These diodes exists as a reliability feature to permit continued operation should any one, two, or three of the individual cells go bad or fail to make contact. Be certain that each battery is inserted correctly. If desired the total battery pack voltage can be checked with a voltmeter. Reposition the Velcro as snug as possible as extra insurance that the batteries will stay in their respective holders.

Slip the battery pack into the housing keeping the end of the battery pack with the red and black connecting wires oriented to the outside. Dress all wires to the side of the battery pack. The battery holder BH-60L has a long tie wrap “tail” on one end. This is the end with the red and black connecting wires and this is the end that goes in last. This long tie wrap (“tail”) can be pulled on for the next battery pack access.
Prepare the end plug using o-rings that have been inspected for nicks and cuts. O-rings are rubber and can ‘rot’ with time and exposure. Slightly stretching them while inspecting them can reveal defects. The three o-rings used are #223 Buna N 70 durometer. 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 McMaster-Carr and others .
Replace the end plug. Replace the ¼-20 button head screws being careful not to cross thread them. Do not over tighten them as the housing is a PVC plastic and does not have the strength of a metal.

B. Installing a new erosion release link:

Obtain a new link with its o-ring groove greased with Silicon grease followed by putting its o-ring in place. (13/16 OD, 9/16 ID 0-ring #207 BUNA 70)
Verify the presence of the two small unpainted places at the base of each upside down ‘U’ shaped release loop. At these points the metal of the loop must be directly in contact with the salt water at the time of release. As an extra precaution verify that the metal isn’t covered with any hard to see coating of some sort by scraping part of it to inspect it (small 1/16 inch tip long nose pliers works well or use a small knife blade to scrape a part of it to inspect it).
Remove the ‘L’ shaped pin that holds the expired link in place.
Remove the expired link while avoiding pulling the attached tinned braided wire out more than 8 inches. (If pulled too far then the larger braided wire further down inside that is attached to it may be pulled out and have to be tucked back into the bottom third of the cavity with an improvised push tool. A plastic or wood 3/8” dowel works to push the braided tinned copper wire back in place.)
Remove the #8 nut and bolt that attaches the link electrically to the release unit.
Replace the link with the two #8 lugs held together with a #8 nut and bolt and an internal tooth lock washer between the two lugs to insure reliable contact. Align the two #8 lugs in a straight line so they will poke down the center of the cavity without hanging up on the internal ledge inside the cavity. Verify that they are tight for reliable electrical contact (critical for release).
Apply silicon grease to the bore.
Carefully insert the link insuring that the two lugs with their nut and bolt pass into the center of the cavity. (Avoid forcing to avoid scratching the o-ring sealing bore surface and avoid loosening the #8 bolt, lock-washer, and nut.)
Replace the ‘L’ shaped securing pin. (It passes through the link-holder and through the link to hold the link in place.)
Replace the two o-rings acting like rubber bands to retain the ‘L’ shaped securing pin. If there is a chance of something rubbing this area during deployment then the ‘L’ shaped pin can be further secured using tape over the o-rings.

C. Verify that the release unit is operating:

Short the water contacts (the two acorn nuts) together with a wire to turn the release unit on. The led will flash its unit identification code (see elsewhere herein) for about 30 seconds and then go into listening mode. In listening mode it will flash the led every 11.5 seconds +/- 30%. Verify this.
Optionally perform in-water or in-air tests on the release unit using the interrogator with its transducer connected. The release unit can be placed near by in air. Any of the commands can be checked. In still water the ‘Brief Erosion’ action can be selected if the unit is very close (watch for bubbles on the coil water contact). In air the full release can be checked [put a voltmeter with or without a 33 ohm 10 watt resistor load between the link (positive) and "coil" (negative). With alkaline batteries verify greater than 14 volts. With Lithium L91 size AA batteries verify greater than 16 volts.
The short across the water contacts (the two acorn nuts) can be either removed or left in place for final deployment. (These contacts exists only so that the unit can be turned off when not in use and also so that the long 15 minute release command can be interrupted during checkout to save operator time.) Having these contacts makes it impossible for the operator to forget to turn the unit on when the unit is deployed in water.

D. Final deployment:

Note the release unit’s four digit unit identification number needed for sending it commands.
Attach the release unit in the specific deployment configuration. If it is desired to balance the load between the two loops on the erosion link then one way to achieve this is the following: Use a ¾ inch diameter stainless steel ring and a 24 inch piece of small size extra strong line such as 1/16 inch Spectron. Loop the 24 inch line separately through each loop on the erosion link and through the ring such that the load is distributed evenly to the two loops on the erosion link and does not bend the loops. To achieve this pass the 24 inch line through the ring, through one erosion link loop, through the ring a second time, through the other erosion link loop, and then tie the two ends of the line together. A square knot in Spectron line will slip; so add extra half hitches and further secure the two loose ends by melting them with a small flame such as from a cigarette lighter There are many possible deployments. Beware of such problems as the ring snagging on something after it is released, etc.
Verify that no metallic material is touching the link (ex. a metal hook) as this could radically extend the erosion time and even prevent a release.
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.
Verify that the ships RADAR is off (not likely a problem, but a worthwhile precaution with the high power focused beam from RADAR).

TRANSMITTING COMMANDS:

Hookup of the acoustic release interrogator (command unit):

Supply 12 VDC from a gel-cell battery or equivalent (needs 12 VDC at 5 amps for transmit, but only 13 ma when not transmitting). Connect the transducer to the interrogator and place the transducer in the ocean or near the release unit if in air. If testing is done in air the range readings will be 5 times greater then the indicated range and occasionally poor results may occur. If poor results are observed then try moving the transducers relative position slightly. Ranges up to 20 feet in air are typical.

Operation of the interrogator:

Use the Stop (S) key to break out of the initial power up banner and get to the main menu. Use the Next (N) key to move to the next item on the menu and the Accept (A) key to accept an item from the menu. Likewise for the Select Action sub menu. First, select the underwater unit identification number using the Select unit Id menu item. Second, select the action desired using the Select Action menu item. Third, Transmit the command using the Transmit once or Transmit loop menu item. Transmit once sends the command just once and then automatically switches over to the receive mode or the range display mode if appropriate. Transmit loop sends the command repeatedly without the switchover. Transmit loop should only have to be used if acoustic transmission conditions are marginal for some reason and if so will save operator time.

An example of sending the command ‘Release with Range’:

Supply 12 VDC to the interrogator. 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 selection action sub menu. Use the N key repeatedly to get to ‘Release w Range’. 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 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. In this case of ‘Release w Range’ it will automatically switch over to the ranging mode to interrogate and display the range.

All of the other command setups and transmissions are similar to this one.

Action = Pinger:

Sending this action command causes the release unit to behave like a pinger for 60 seconds until it times out. While acting as a pinger it emits a single 20 ms ping once per second (1.00 sec +/- 2%). These pings can be picked up on a pinger receiver or by the interrogator set for Receive Pings. If a pinger receiver with tracking antenna is available the direction to the release unit can be obtained.

Action = Range Enable:

Sending this action command causes the release unit to behave like a transponder for 60 seconds until it times out. While acting as a transponder it listens on frequency FM for a pulse, delays 40 ms, and then replies on frequency FR with a return pulse. [After this action command is sent the interrogator must be put into Range Display mode. If Transmit Once was used it automatically switches to this mode. If Transmit Loop was used then Transmit Loop must be stopped with the Stop (S) key and then the Next (N) key be pressed to reach Range Display then the Accept (A) key pressed.] With the interrogator in Range Display mode the range is displayed in feet from 0 to 10,000 feet. If no signal is received it displays ‘No reply signal’. Remember that the transponder action by the release unit times out 60 seconds after it received the Range Enable command. Accordingly, if additional ranging is desired the command must be repeated.

Action = Battery Report:

Sending this action command causes the release to put a 60 ohm (about 240 ma) load on the battery for 2 seconds. Just before the end of the 2 seconds the battery voltage is compared with voltage references to determine whether the battery is High, Medium, or Low. This information is then sent to the surface via the time spacing between pings. This can be timed with a stop watch by listening to a pinger receiver or observing the signals received by the interrogator. The following table gives the battery voltage for the three different ping spacings:

Ping Spacing	Battery State	AR-60-E (12 size AA cells)
2.00 sec	High Battery	> 1.3 volts/cell (> 15.6 volt total)
3.00 sec	Medium Battery	1.1 to 1.3 volts/cell (13.2 v to 15.6 v total)
4.00 sec	Low Battery	< 1.1 volts/cell (< 13.2 volt total)

(Note: On units sold prior to 7-1-02 the trip voltages were 1.1 and 0.9 instead of the above 1.3 and 1.1. )

Release unit time-out times:

The following time-outs are used to free the release unit for another command:

Pinger Action = 60 sec (one ping per sec). Battery Report = 30 pings (60 sec on high battery). Range Enable = 60 sec. Fast Ping Check = 2 sec. Brief Erosion = 10 sec. Release with range = 15 min. Release with ping = 15 min.

STORAGE:

Keep a new or used erosion link installed on each release unit when storing to keep dirt and water out of the replaceable link cavity. Store out of direct sunlight. For electronic "burn-in", in attempt to cause any unknown marginal semiconductors to fail while not deployed, keep the unit on. Do this by using a wire across the water contacts (acorn nuts). This keeps the unit in receive mode where it draws about 180 micro Amperes (consuming alkaline batteries in about 12 months). However, if it is desired to not drain the batteries then keep the unit off by having no wire and washing any salt off the area near the water contacts and keeping this area dry and free of anything with a conductivity that is greater than a what a 10 meg ohm resistor would be.

SAFETY WARNINGS:

Use extreme caution when removing release links since a leak could have created compressed air in the link cavity which could shoot the link out when the ‘L’ shaped securing pin is removed.

Remove the housing end plug with extreme caution for the same reason.

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 forms on it which can be left there or occasionally brushed off.

EROSION TIME VS. WATER TEMPERATURE:

Lab tests indicate that the full time for release erosion 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 75% as the battery voltage decreases from 18 volts to 12 volts. The erosion time increases about 200% (3x) as the battery voltage drops from 12 volts to 6 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 so some accidentally deposited grease is very unlikely to cause a problem.

LINK CAVITY LEAK:

Should the link cavity 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 be found to be full of water (and possibly air pressure; see SAFETY WARNINGS herein) inspect the tinned braided wire inside the cavity for adequate integrity for future use.

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 the current action (such as release with range) and the unit returns to listen mode. If this should happen the pinging will stop and the topside unit can be used to interrogate the state of the battery, wait for the batteries to recoup a bit, or try again. If trying again is selected consider sending a less current using command such as the Brief Erosion one. 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:

RECEIVERS:

Both the release unit receiver and the interrogator receiver utilize a low noise wide band first stage directly driving a classic over coupled L/C double tuned circuit. This directly connected combination amplifies in-band signals about 60 dB but out-of-band signals very little. This combination operating at a low signal level acts to prevent saturation of the receiver by strong out-of-band signals. The double tuned circuit is followed by about 30 dB of gain driving a single tuned circuit. This is followed by another 30 dB of gain from an amplifier circuit with symmetrical limiting. The symmetrical limiting is important for supplying consistent signals to the following three detector circuits. Each detector circuit is made with an L/C tuned circuit and provides a dc level output proportional to the energy in its frequency band. The energy in the two outer bands is combined and is continuously compared with the energy in the center band using the detector dc levels and a comparator. When the energy in the center band exceeds the energy in the outer bands for 8 milliseconds an output line changes state indicating the presence of a signal. This circuit has excellent sensitivity, excellent rejection of strong out-of-band signals, operates correctly at all signal levels and draws only about 2 milliamps when on.

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 times 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 are wrong the unit immediately goes back to listening mode. Here it will not respond to the additional 20 ms pulses.

RELEASE UNIT RELEASE MODE:

When the release command is received the micro controller puts a line high for the release for the duration of the release mode time-out time (e.g. 15 min). During this time the full battery voltage (minus a diode drop and a sense resistor drop) is applied to the link (+) relative to the "coil" (-) water contacts. The current flow is approximately one Amp for a LKH-162 link with its four 0.035 inch diameter by 0.1 inch long exposed points. A current limiting circuit limits the current to approximately 1400 mA and a thermal shutdown circuit will temporarily shut down all current flow if the temperature of the TO-220 pass P-Channel FET exceeds approximately 85 degree Centigrade. A short across the link to "coil" will not damage the release unit. The thermal shutdown will keep recycling and continue to supply current should the erosion current be inordinately high. (This assumes that the battery voltage doesn’t drop below 6 volts at which time a friendly reset of the micro controller would occur and a new command would have to be sent to restart the erosion).

NOTES REGARDING THE CHECKOUT OF AN AR-60 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 12 bits in binary. This number can be retrieved 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 (or remove the short across the two acorn nut water contacts). 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 across the water switch terminals until the unit starts flashing. Write down the flash counts (ex. 11 11 11 1 11 1 11 11 11 1 11 1). Convert these to decimal (ex. 0133). 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 has been placed there. Note that the unit Id goes with the electronics inside and not the housing tube or end plug should parts ever be swapped. Unit Identification Numbers are assigned by Sub Sea Sonics. This eliminates unit identification switches with their possibility of switch contact failure.

Listening Mode Of Release: When the release unit is turned on (submerged or a wire placed across the two acorn nut contacts on the plug end) 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 LED42 flash inside the unit or by observing the outside led on the hydrophone end plug flash one tenth as often which is every 11.5 sec +/- 30%.

Actions By Release: When a command is sent by the Acoustic Release Interrogator, the release will ping or 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 ping and/or flash with normal brightness to indicate which command it received as per the following:

One ping/flash every 1.00 sec (60 sec total) => Pinger Action.

One ping/flash every 2.00 sec (30 total) => Battery High.

One ping/flash every 3.00 sec (30 total) => Battery Medium.

One ping/flash every 4.00 sec (30 total) => Battery Low.

20 very fast ping/flashes => Fast Pinger Check (2 sec).

100 very fast ping/flashes => Brief Erosion Check (10 sec).

One ping/flash every 1.50 sec (for 15 minutes) => release with ping.

These actions can only be interrupted by removing from water or removing the jumper wire across the water contacts. This must be followed by waiting for the unit to check the water contacts. This occurs every 11.5 sec +/- 30% for all but the 15 minute releases which require 60 seconds between 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 a release 15 minute action before it times out can save a lot of time in system checkout.

ACOUSTIC RELEASE SYSTEM SPECIFICATIONS:

AR-60-E:

Acoustic release using fast electrolytic erosion of stainless steel for the release.

Multi-path interference resistant by use of:

· Single frequency sent at any one time.

· Pulses spaced at least 1.0 seconds to permit echo die out before the next pulse.

· Suppression frequency spectrum transmitted to block echoes, noise, and interference.

· Long pulses used (20 ms or greater) for ample energy integration time.

Reception frequency bands (one detector for each of the three):

Main signal band 35714 Hz +/- 3% (center 1/28 us) FM.

Lower inhibit band 33333 Hz +/- 3% (lower 1/30 us) FS.

Upper inhibit band 38462 Hz +/- 3% (upper 1/26 us) FR.

Reception sensitivity: 0.5 micro volt rms with a 3000 ohm driving impedance for a logic level solid transition. (-37 dB relative to one micro bar.)

Reply frequency for pinging mode, transponder mode, and all other replies:

Single reply frequency 38462 Hz +/- 1% (FR).

Acoustic output: 1 watt (171.5 dB relative to 1 micro Pascal at 1 meter).

Command reception: Seven pulses accurately time spaced preceded by a wake-up/synchronization 2.5 sec steady signal all on frequency FM and each pulse preceded by suppression frequency FS.

1000 ft max. rated depth (1500+ ft design)

260 lb. max. rated release load capability limited further by the specific release link used.

Housing made from 2 inch nominal schedule 80 PVC pipe (2.375 inch OD).

Total length 31 inches. Weight 4.4 pounds in air; near neutral in water.

Accepts link LKH-162 (160 lb) or link LKH-262 (260 lb).

Battery current average in listening mode is 180 micro amps typical, 200 micro amps maximum.

Battery life using a single string of AA alkaline cells is 6 months. Using L91 lithium batteries the life is 2 to 3 times this. (Assumes 50% for listening and 50% for five 200 mA-hr LKH-162 releases).

Operates down to 6 VDC with a friendly reset if battery goes below this. (But don’t let batteries get this low).

Accepts BH-60L battery holder for 12 alkaline or lithium ‘AA’ cells. Features a diode across each cell to permit continued operation should 1, 2, 3, or even 4 cells fail or fail to make contact.

Unit is reverse battery protected via a series diode.

Unit output is short circuit proof via thermal shutdown and automatic retry.

All unit external contacts are electrostatic discharge resistant and have passed a test during design checkout of 30 kV from a 25 pF capacitor..

AR-60-M: (In development – not available at this time – estimated initial price $2370)

Acoustic release with same acoustics signals and coding scheme as used on the AR-60-E above. Unit uses a 500 oz-in electric gear motor to effect the release. The motor turns a shaft having one O-ring seal that unscrews a special nut which is secured to the released line (a worm drive like action driving off the release special nut).

1000 ft max. rated depth (1500+ ft design)

260 lb. max. rated release load capability (300+ lb. design)

This release, AR-60-M will work in fresh water whereas the erosion link type, AR-60-E will not. This release will work in contaminated water with extremely rapid bio-fouling whereas the erosion link type if completely covered probably will still work but conceivably might not. Housing made from 2 inch nominal schedule 80 PVC pipe. Length approximately 35 inches.

ARI-60:

Acoustic release interrogator (for use with AR-60-E or AR-60-M).

Command transmission: Seven pulses accurately time spaced preceded by a wake-up/synchronization 2.5 sec steady signal all on frequency FM and each pulse preceded by suppression frequency FS.

35714 Hz +/- 0.1% 20 ms pulse used as the main frequency, FM.

33333 Hz +/- 0.1% 20 ms rapid pulse used to generate the suppress frequency spectrum, FS.

Acoustic output: 10 watt (181.5 dB relative to 1 micro Pascal at 1 meter).

Reception frequency bands (one detector for each of the three):

Reply signal band 38462 Hz +/- 3% (center 1/26 us) FR.

Lower inhibit band 35714 Hz +/- 3% (lower 1/28 us) FM.

Upper inhibit band 41667 Hz +/- 3% (upper 1/24 us) FI.

Reception sensitivity: 0.5 micro volt rms with a 3000 ohm driving impedance for a logic level solid transition. (-37 dB relative to one micro bar.)

Requires 12 volt 5 amp DC supply (user supplied).

Unit identification number selected using Increase/Decrease keys.

Action selected using Next/Accept keys with an LCD display.

Transmit command selected from Menu using Next/Accept keys.

TD-60:

Transducer for the ARI-60 interrogator. Made from a piezoelectric cylinder 1.0 inch OD by 0.5 inch high by 0.115 inch thick walls. Full electrostatic shield. Normally supplied on a 50 foot cable with a BNC connector. It can be modeled with a 4.7 nF capacitor and a 3000 ohm resistor in parallel. Its in circuit electrical ‘Q’ is about four making the tuning of the resonant transformer that drives it not critical.

BH-60L:

Battery pack for AR-60-E erosion release. Uses nylon battery holders with a 2 amp diode wired across each 'AA' battery to permit continued battery pack function in the event of a one, two, three, or even four cell or cell contact failure. Holds 12 ‘AA’ size cells. Either alkaline or lithium (Eveready L91) cells can be used. Note that if the user happens to insert any one cell backwards the respective diode (plus a resistor in series with it) will get hot and the backwards battery will discharge fast. So be extra careful to insert each battery cell with the correct polarity and optionally cautiously feel each diode on the BH-60L to insure that none of the cells were inserted backwards.

LKH-162:

Release link for AR-60-E. One use only. Load rated at 160 lb. on-axis load. Design load 300+ lb. on-axis. Eroding strength members are four pieces of 0.035 inch diameter stainless steel 316L wire configured as two loops of wire. Measured erosion time 6 minutes at 1000 foot depth.

LKH-262:

Release link for AR-60-E. One use only. Load rated at 200 lb. on-axis load. Design load 300+ lb. on-axis. Eroding strength members are four pieces of 0.045 inch diameter stainless steel 316L wire configured as two loops of wire. Estimated erosion time is 12 minutes at 1000 foot depth. Note: If erosion happens to take longer then 15 minutes it may be necessary to send the release command a second time to finish the erosion. (The AR-60-E applies the erosion voltage for exactly 15 minutes upon receipt of the release command).