[1] Initial Send Sequence Number - Identifier unter TCP/IP, erste gesendete Sequenz bei einer Verbindung

[2] Integrates Switching System

[3] Information Storage System (->"IEEE Standard Dictionary")

[4] Input Subsystem (->"IEEE Standard Dictionary")

[5] CERT Internet Security Scanner/Systems (http://iss.net/)

[6] International Switching Symposium World Telecommunication Congress (IEEE/VDE)

[7] Imaging Science Subsystem (Cassini Orbiter, NASA, http://www.jpl.nasa.gov/cassini/) {Astronomie}

[8] International Space Station (vergl. 2.)) {Weltraumfahrt}

[9] Instruction Set Simulator

[10] Internet Selling System

[11] Wiscasset, ME, USA -internationale Fughafen-Kennung