Powerful electronic lockpick. Strangely enough, it does not seem to be an all-purpose thieves' instrument. Rather, it seems to have been created with a specific electronic lock in mind and can't be used to override anything else.Ingame description
The Decoder is a mission item featured in S.T.A.L.K.E.R.: Shadow of Chernobyl.
A special device assembled by Fang. Made in order to open a secret door within the Sarcophagus of Reactor #4. The Decoder is made up of parts from old army cryptographic machines. Fang assembled two decoders using parts he bought from Sidorovich, some diggers at the Garbage and from Freedom. During S.T.A.L.K.E.R.: Clear Sky, Strelok's Group placed two decoders in a stash near the Brain Scorcher when they proceeded to the center. The first decoder was most probably destroyed and the second one was left in an apartment in Pripyat. Strelok discovers this decoder during the events of S.T.A.L.K.E.R.: Shadow of Chernobyl, and uses it to decode the door in the Sarcophagus.
The one and only, remaining specimen is found in of the apartments in Pripyat during the course of the game.