High Quality Content by WIKIPEDIA articles! T.61 is an ITU-T recommendation for a Teletex character set. T.61 predated Unicode, and was the primary character set in ASN.1 used in early versions of X.500 and X.509 for encoding strings containing characters used in Western European languages. While T.61 continues to be supported in modern versions of X.500 and X.509, it has been deprecated in favor of Unicode.