Before revision: The first digit denotes the p-n junction count ("3" may also denote a dual-gate FET); then follows the letter "S", then: 2nd letter Type of semiconductor<none>DiodeAhigh frequency PNP BJTsBaudio frequency PNP BJTsChigh frequency NPN BJTsDaudio frequency NPN BJTsEDiodeFThyristorGGunn diodeHUJTJP-channel FETs (both JFETs and MOSFETs)KN-channel FETs (both JFETs and MOSFETs) MTriacQLED RRectifierSSignal diodeTAvalanche diodeVVaricap ZZener Diode Then follows the Japan Electronics and Information Technology Industries Association's Electronic DEvice REgistration Center (JEITA-EDEREC)-assigned part number, optionally followed by suffixes (such as "A", "B", "C", or "R", "O", "BL", standing for "Red", "Orange", "Blue" etc.)
After revision: The first digit denotes the p-n junction count ("3" may also denote a dual-gate FET); then follows the letter "S", then: 2nd letter Type of semiconductor<none>DiodeAhigh frequency PNP BJTsBaudio frequency PNP BJTsChigh frequency NPN BJTsDaudio frequency NPN BJTsEDiodeFThyristorGGunn diodeHUJTJP-channel FETs (both JFETs and MOSFETs)KN-channel FETs (both JFETs and MOSFETs) MTRIACQLED RRectifierSSignal diodeTAvalanche diodeVVaricap ZZener Diode Then follows the Japan Electronics and Information Technology Industries Association's Electronic DEvice REgistration Center (JEITA-EDEREC)-assigned part number, optionally followed by suffixes (such as "A", "B", "C", or "R", "O", "BL", standing for "Red", "Orange", "Blue" etc.)