Principle of operation:
The object is gripped with fishing collet during coil tubing unloading. At first, the collet is retracted into the body, compressing a spring and thus opening. Once opened wide enough it grabs an object, which is then retrieved by coil tubing pulling.
The detachment of the overshot is carried out by pressure increase in coil tubing over 50 atm. The excess pressure is created by increase of fluid flow through the overshot. At the same time a pressure difference at the outlet is created, that moves collet off the caught object.