The Model 1090ET Transponder is a microprocessor controlled modification of the Model 1090E Acoustic Release. The 1090ET provides a reliable and secure acoustic link permitting the relocation of instrument packages or other items from underwater locations up to 8,000 meters deep.

The transponder receives coded acoustic signals and processes them. If the received code matches any one of the commands performed by the transponder, the microprocessor performs that function.

The functions performed by the 1090ET are:

1. Rearm - the "rearm" code rearms the transponder mechanism and disables the transponder reply electronics (Four frequency codes starting with letter "C" or "D").

2. Enable - the "enable" code activates the transpond reply electronics (First three frequency codes of the rearm code).

Once the transpond reply electronics are enabled, an interrogate signal, transmitted from an InterOcean Model 1100E Surface Acoustic Command Control Unit, will generate a reply signal from the transponder. This reply signal can be used for relocating or tracking an attached instrument package.