The need to know where our own units are, the opponent units and where the neutral are is important to avoid accidental fire and to operate efficiently. The most important thing to achieve this, is to have a good and current situation awareness. As a support to achieve this, is various technical solutions and a secure connection. Today, voice communication is one of the most important means of achieving this situation awareness, along with transmission of the position from control centers. Although IFF systems today is only considered to be a complement to create this situation awareness, so can appropriate systems correctly used be of great help in different situations. Besides recognition marking equipment in the army, the IFF in the air Force and partly the Navy the most common IFF system. It is not only technical solutions that needs to achieve a good situation awareness. But also the use of the various systems and methods need to be trained and coordinated within and between the arms branches to get a mutual understanding of the systems and interpret them right. As well as training on what happens if the connection is broken, jammed or misled. To handle this you also need an understanding of how the battle is, to thus safer assess where it is likely that friend or enemy may be. The trends on the technical side is that development occur mainly in radio communications and automatic target recognition (ATR). In radio communications, the general trends is in higher bandwidth, better suppressor and stronger encryption and robustness in difficult environments such as urban and indoor. Other trends are transition to software radio, surreptitious links, jamming and decoy, and authentication of the sender. ATR is an area that are developing more and more, by benefiting from the developments in the areas of radar technology, optics, electronics, and better and more advanced algorithms for analysis. This report describes a literature review of developments and trends in a number of technology for IFF. The report concludes with a discussion and some conclusions about IFF systems, from a technical and non-technical perspective.