ISDN telephone sets with advanced voice functions
Yutaka Nishino, Toshihiro Naganawa, Rempei Sawada, M. Kasai, Kazukani Koga · IEEE Transactions on Consumer Electronics · 1991
Three types of ISDN (integrated services digital network) telephones and LSIs for ISDN telephones have been developed. These telephones feature improved functions using network information and ciphered voice communication using an end-to-end digital link. A low-cost network interface sector that uses LSI with layer 1 to 3 control functions and related software is incorporated. Also, an analog I/O sector was incorporated together with a codec onto a single chip. Low-power-consumption designs for all circuits enable operation with line-fed power for a telephone set, thereby securing communication in times of emergency.>