Underwater Timed Release System

This underwater release system is used to release one or more lines underwater after a specified period of time. It is commonly used for the release of a float and coil of line that is attached to an object of interest. System features high timing accuracy.

Click on the photos below for detailed descriptions.

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  1. Worst case timing error of +/- 2 minute per month to initiation of release.  (Upon initiation of release it takes an additional time of 10 to 20 minutes for the erosion to complete and the associated release to occur.)
  2. User selectable time-until-release from zero to 170 days in 7.5 minute steps.  ( Model TRP-45C)
  3. Adjustable time-until-release (TUR) by pressing the INCREASE or the DECREASE switch on the programmer (TRP-45C).
  4. Simple programming of a release unit by first setting the desired time-until-release (TUR) in the programmer, selecting ‘Transfer time into release.’ from the menu, pressing the ‘ACCEPT’ switch and then touching the two contacts  to the release.  Within 3 seconds the transfer is complete and the message ‘Successfully programmed unit.’ is displayed.
  5. Full verification upon each programming that the time-until-release (TUR) transferred correctly.
  6. During programming the batteries in the release are measured under load and the voltage displayed.
  7. A release unit can be reprogrammed at any time.  Timing starts at the moment of programming or re-programming.
  8. Many release units can be quickly programmed to the same time delay.
  9. Simple replacement of an expired erosion link by unscrewing retainer cap on the release.
  10. Only need to stock one kind of erosion link which is good for all time-until-release times.
  11. Operating depth is 0 to 800 feet (244 meters).
  12. Release uses three Lithium L91 Energizer AA batteries (in series).  They should give an average of over 50 releases over a period of four years of continuous use (in timing mode) without having to change them (assumes using the LK-40 release link).  They have a manufacturer claimed shelf life of 14 years (i.e. good after 14 years if not used). For less intense use they should be good for eight years if unit is in timing mode 50% or less of the time (e.g. Programmed for two months then not used for two months, programmed for two months then not used for two months, etc.).
  13. Battery contact failure in the release is prevented by using welded connections (or special battery-specific soldered connections). (Note:  A special battery replacement procedure is required but is unlikely to be needed due to the long battery life of the unit).
  14. Programmer uses two 9 volt alkaline batteries of the commonly available type.  One set of programmer batteries are good for 50 hours of continuous use.  An auto shutoff makes programmer battery usage negligible.


This release unit is deployed underwater and contains a micro computer and batteries and holds a replaceable release link with a screw on retainer cap.  It is programmed to the time-until-release (TUR) desired by electrical contact with the contacts on a programmer before deployment underwater.  Release accuracy is +/-2 minute per month.  After time is up and release erosion initiates it takes typically another 10 to 20 minutes for the link erosion to complete with link LK-40 (15 to 30 minutes for link LK-80). (Note: This release works in ocean water and typical bay water.  It will not work in fresh water since the electrolytic erosion will not occur at a fast enough rate).


The release link is made from metal wire encapsulated in a holder.  The release link effects the release by fast electrolytic erosion of the exposed metal part of its hoop thereby freeing any line passed through it.  This occurs when a positive voltage is connected to it by the internal electronic timer. It is partially coated with an epoxy coating to restrict the intended erosion to two points at the base of the hoop.  This speeds the release and saves on battery consumption.  The release links are replaced after each release.  An O-ring is used to keep salt water out of the contact cavity.  See menu item ‘Release Links’.


This programmer is used for entering the desired time-until-release (TUR) into the release unit.  It has an LCD display (two 16 characters rows).  It holds the time-until-release (TUR) as set using an ‘INCREASE’ / ‘DECREASE’ momentary switch.  Once set this time-until-release (TUR) is transferred to a release unit (TR-45) by hand held contact.  At this moment the timing starts.  The display reports ‘Successfully programmed unit.’ only if programming was successful including verification.  Immediately after programming, the display shows the battery voltage of the release batteries (tested under electrical load).  NOTE:  The timer release unit (TR-45) can be re-programmed at any time.

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