What are the definitions for Class I and II line supervisions?
DCID 6/9 defines the classes of line supervision as: CLASS I: Achieved through the use of DES or an algorithm based on the cipher feedback or cipher block chaining mode of encryption. Certification by NIST or another independent testing laboratory is required. CLASS II: Refers to systems in which the transmission is based on pseudo random generated or digital encoding using an interrogation and response scheme throughout the entire communication, or UL Class AA line supervision. The signal shall not repeat itself within a minimum six month period, Class II security shall be impervious to compromise using resistance, voltage, current, or signal substitution techniques.
